Method and system for variable displacement engine diagnostics

ABSTRACT

Methods and systems are provided for diagnosing a cylinder valve deactivation mechanism in an engine system having cam-actuated valves. Movement of a latch pin of the deactivation mechanism is inferred from an induction current generated by a solenoid coupled to the latch pin, and the inferred movement is used to diagnose operation of cylinder valve deactivation mechanism. The inferred movement and a profile of the induction current is also used to estimate camshaft and crankshaft timing for improved cylinder fuel delivery in the absence of a camshaft sensor.

FIELD

The present application relates to methods and systems for monitoringactuation of a cylinder valve deactivation mechanism in a variabledisplacement engine (VDE).

BACKGROUND/SUMMARY

Engines operating with a variable number of active or deactivatedcylinders, also referred to as variable displacement engines (or VDE),may be used to increase fuel economy while optionally maintaining anoverall exhaust mixture air-fuel ratio about stoichiometry. In someexamples, half of an engine's cylinders may be disabled during selectedconditions, where the selected conditions can be defined by parameterssuch as a speed/load window, vehicle speed, etc. In still otherexamples, cylinders may be individually and selectively deactivated.

A VDE control system may disable selected cylinders through the controlof a plurality of cylinder valve deactivators that affect the operationof the cylinder's intake and exhaust valves. Various mechanisms may beused to enable cylinder deactivation. One example of a cylinderdeactivation mechanism includes hydraulically actuated latches coupledto rocker arm assemblies to implement zero valve lift and cylinderdeactivation. For example, switching roller finger followers (SRFF) mayuse hydraulically actuated latches. In these systems, hydraulic pressure(such as pressurized oil from an oil pump) may be used for latchactuation. One example valve deactivation mechanism is shown by Hugheset al in US 20170183982. Therein, valve operation is adjusted via arocker arm assembly that includes a latch pin mounted on a rocker arm.The latch pin is actuated via an electromagnet. Movement of the latchpin into or out of the rocker arm assembly affects an activation stateof the corresponding valve.

The inventors herein have recognized that cylinder valve deactivationmechanisms need to be periodically diagnosed to ensure that the fueleconomy benefits of operating in a VDE mode can be extended. Inaddition, valve operation in deactivatable cylinders may need to bediagnosed to ensure proper switching between active cylinder anddeactivated cylinder modes. Diagnostic methods that enable the cylindervalve deactivation mechanism to be directly assessed while switching thecylinder between active and deactivated states are particularlybeneficial. However, one issue with such a diagnostic is that itrequires the engine to be transitioning states, such as where a givencylinder is activated or deactivated. Since the transitioning is basedon engine speed-load conditions, which continually change over thecourse of a drive cycle, there may be extended periods of a drive cyclewhere there is no VDE transition. Consequently, the opportunities forperforming the diagnostic may be limited. If a VDE mode is activelyenforced during the drive cycle to complete a diagnostic, engineperformance may be affected. For example, if a VDE mode is imposed athigh load conditions, torque demand may not be met. In addition, it maynot be possible to complete the diagnostic at high engine speeds due toinsufficient time being available to actuate the cylinder valvedeactivation mechanism.

In one example, the issues described above may be addressed by a methodfor an engine comprising: latching and unlatching anelectrically-actuated latch pin of a cylinder valve deactivationmechanism coupled to a valve of a cylinder as engine load varies; andindicating degradation of the cylinder valve deactivation mechanismbased on inferred latch pin movement during the latching and unlatching.In this way, VDE diagnostics may be completed without intrusivelychanging a VDE state of the engine.

As one example, an engine system may include cylinders having valvesthat are selectively deactivatable via a cylinder deactivation mechanismthat includes a latch pin mounted on a rocker arm assembly. On a givendrive cycle, as engine speed and loads change responsive to drivertorque demand, the engine may be continuously varied between various VDEand non-VDE states by adjusting cylinder deactivation mechanisms coupledto individual cylinders. For example, when the engine load drops below athreshold, an engine controller may apply a voltage pulse to energize asolenoid coupled to the latch pin to move the latch pin out of therocker arm assembly, thereby deactivating the corresponding cylindervalve (and moving to a VDE state). Likewise, when engine load risesabove the threshold, the engine controller may apply the voltage pulseto energize the solenoid coupled to the latch pin to move the latch pininto the rocker arm assembly, thereby reactivating the correspondingcylinder valve (and moving to a non-VDE state). Latch pin movementduring the latching and unlatching may be inferred based on a measuredelectric current signature, which may include a number and (relative)position of peaks and valleys in the electric current signature, as wellas slope of the current. For example, the presence of latch pin movementmay be inferred from a signature that includes a temporary currentdecrease (e.g., to a valley) as voltage is applied (e.g., a change inthe slope of the current). Based on the presence or absence of latch pinmovement, the cylinder valve deactivation mechanism may be diagnosed.For example, the solenoid may be energized when the cam is at the basecircle, and so the latch pin is expected to be able to freely movebetween active and deactivated positions. Thus, if latch pin movement isnot observed while at this position, it may be inferred that themechanism is degraded. Accordingly, appropriate mitigating actions maybe undertaken based on whether cylinder valve is active or deactivatedwhen the degradation is inferred.

In this way, by correlating the electric current signature of a solenoidto the movement of a latch pin, a cylinder valve deactivation mechanismmay be reliably diagnosed. The technical effect of performing thediagnostic while an engine speed-load is changing is that the diagnosticcan be completed non-intrusively. By completing the VDE diagnostic, thelikelihood of engine error states (such as misfires) that may betriggered by a degraded VDE mechanism are reduced. By performing thediagnostic non-intrusively, the likelihood of completing the diagnosticon a drive cycle is improved. By timely diagnosing a VDE mechanism, thefuel economy benefits of cylinder deactivation can be extended over alarge range of engine operating conditions.

It should be understood that the summary above is provided to introducein simplified form a selection of concepts that are further described inthe detailed description. It is not meant to identify key or essentialfeatures of the claimed subject matter, the scope of which is defineduniquely by the claims that follow the detailed description.Furthermore, the claimed subject matter is not limited toimplementations that solve any disadvantages noted above or in any partof this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic depiction of an engine system of a vehicle.

FIGS. 2A-2D shows an electric latch rocker arm mechanism that may beincluded in a valve deactivation mechanism.

FIG. 3 is a table summarizing a relationship between cam timing, latchpin position, valve state, and an ability of the latch pin to move.

FIG. 4 shows a high-level flow chart of an example method forcontrolling cylinder valve operation during operation of a variabledisplacement engine.

FIG. 5 shows a flow chart of an example method for deactivating andreactivating cylinder intake and exhaust valves during a transition toand from a VDE mode of operation using an electric latch rocker armmechanism.

FIGS. 6A-6B shows a flow chart of an example method for diagnosing anelectric latch rocker arm mechanism when a change in an operationalstate of a corresponding valve is commanded.

FIG. 7 shows a flow chart of an example method for diagnosing anelectric latch rocker arm mechanism during low speed conditions when achange in an operational state of a corresponding valve is notcommanded.

FIG. 8 illustrates an example graph of engine signals generated while acrankshaft is rotated.

FIG. 9 shows a flow chart of an example method for determining camshaftposition via an electric latch rocker arm mechanism when a crankshaftposition is known.

FIG. 10 shows a flow chart of an example method for determiningcrankshaft and camshaft position via an electric latch rocker armmechanism.

FIG. 11 depicts a prophetic example of setting cylinder intake valves toa desired state during an engine start without camshaft positioninformation.

FIG. 12 depicts a prophetic example of transitioning an engine to andfrom a VDE mode of operation using an electric latch rocker armmechanism and diagnosing the electric latch rocker arm mechanism duringthe transition.

FIG. 13 depicts a prophetic example of diagnosing an electric latchrocker arm mechanism during low engine speed conditions.

FIG. 14 depicts a prophetic example of determining a camshaft positionvia an electric latch rocker arm mechanism when a crankshaft position isknown.

FIG. 15 depicts a prophetic example of determining both crankshaft andcamshaft position using an electric latch rocker arm mechanism andoutput of a crankshaft position sensor.

DETAILED DESCRIPTION

The following description relates to systems and methods for controllinga cylinder valve deactivation mechanism of an engine, such as the enginesystem of FIG. 1. The cylinder valve deactivation mechanism may comprisean electric latch rocker arm mechanism, such as the electric latchrocker arm mechanism depicted in FIGS. 2A-2D. For example, by actuatinga latch pin of the valve deactivation mechanism between an engagedposition and a disengaged position via energization of an associatedsolenoid, the corresponding cylinder valve may be switched between anactive and a deactivated state, as summarized in the table of FIG. 3.For example, the latch pin position, and therefore the valve state, maybe changed during an engine startup or shutdown, such as according tothe method of FIG. 4 and illustrated with respect to FIG. 11, and duringtransitions to and from a variable displacement engine (VDE) mode ofoperation, such as according to the method of FIG. 5. However, the latchpin is only moveable when the rocker arm is unloaded, such as when acorresponding cam is engaged with a cam follower while the cam is on itsbase circle. Furthermore, movement of the latch pin may be detectedbased on an inductive signature of the associated solenoid during theenergization. Based on the movement (or lack thereof) of the latch pinand the cam position during the energization, degradation of thecylinder valve deactivation mechanism may be detected, such as accordingto the methods of FIGS. 6A-6B and 7 and as illustrated with respect toFIGS. 12 and 13. Further still, the movement (or lack thereof) of thelatch pin during the solenoid energization may be combined with enginesignals, such as the engine signals illustrated in FIG. 8, to determinecamshaft and/or crankshaft position, such as according to the methods ofFIGS. 9 and 10 and as illustrated with respect to FIGS. 14 and 15. Inthis way, the electric latch rocker arm mechanism may enable valvedeactivation to be precisely controlled as a desired valve statechanges, used to determine or confirm crankshaft and/or camshaftposition, and diagnosed for degradation.

Turning now to the figures, FIG. 1 depicts an example of a cylinder 14of an internal combustion engine 10, which may be included in a vehicle5. Engine 10 may be a variable displacement engine (VDE), as describedfurther below. Engine 10 may be controlled at least partially by acontrol system, including a controller 12, and by input from a vehicleoperator 130 via an input device 132. In this example, input device 132includes an accelerator pedal and a pedal position sensor 134 forgenerating a proportional pedal position signal PP. Cylinder (herein,also “combustion chamber”) 14 of engine 10 may include combustionchamber walls 136 with a piston 138 positioned therein. Piston 138 maybe coupled to a crankshaft 140 so that reciprocating motion of thepiston is translated into rotational motion of the crankshaft.Crankshaft 140 may be coupled to at least one vehicle wheel 55 ofvehicle 5 via a transmission 54, as further described below. Further, astarter motor (not shown) may be coupled to crankshaft 140 via aflywheel to enable a starting operation of engine 10.

In some examples, vehicle 5 may be a hybrid vehicle with multiplesources of torque available to one or more vehicle wheels 55. In otherexamples, vehicle 5 is a conventional vehicle with only an engine. Inthe example shown, vehicle 5 includes engine 10 and an electric machine52. Electric machine 52 may be a motor or a motor/generator. Crankshaft140 of engine 10 and electric machine 52 are connected via transmission54 to vehicle wheels 55 when one or more clutches 56 are engaged. In thedepicted example, a first clutch 56 is provided between crankshaft 140and electric machine 52, and a second clutch 56 is provided betweenelectric machine 52 and transmission 54. Controller 12 may send a signalto an actuator of each clutch 56 to engage or disengage the clutch, soas to connect or disconnect crankshaft 140 from electric machine 52 andthe components connected thereto, and/or connect or disconnect electricmachine 52 from transmission 54 and the components connected thereto.Transmission 54 may be a gearbox, a planetary gear system, or anothertype of transmission.

The powertrain may be configured in various manners, including as aparallel, a series, or a series-parallel hybrid vehicle. In electricvehicle embodiments, a system battery 58 may be a traction battery thatdelivers electrical power to electric machine 52 to provide torque tovehicle wheels 55. In some embodiments, electric machine 52 may also beoperated as a generator to provide electrical power to charge systembattery 58, for example, during a braking operation. It will beappreciated that in other embodiments, including non-electric vehicleembodiments, system battery 58 may be a typical starting, lighting,ignition (SLI) battery coupled to an alternator 46. Alternator 46 may beconfigured to charge system battery 58 using engine torque viacrankshaft 140 during engine running. In addition, alternator 46 maypower one or more electrical systems of the engine, such as one or moreauxiliary systems including a heating, ventilation, and air conditioning(HVAC) system, vehicle lights, an on-board entertainment system, andother auxiliary systems based on their corresponding electrical demands.In one example, a current drawn on the alternator may continually varybased on each of an operator cabin cooling demand, a battery chargingrequirement, other auxiliary vehicle system demands, and motor torque. Avoltage regulator may be coupled to alternator 46 in order to regulatethe power output of the alternator based upon system usage requirements,including auxiliary system demands.

Cylinder 14 of engine 10 can receive intake air via a series of intakepassages 142 and 144 and an intake manifold 146. Intake manifold 146 cancommunicate with other cylinders of engine 10 in addition to cylinder14. One or more of the intake passages may include one or more boostingdevices, such as a turbocharger or a supercharger. For example, FIG. 1shows engine 10 configured with a turbocharger, including a compressor174 arranged between intake passages 142 and 144 and an exhaust turbine176 arranged along an exhaust passage 135. Compressor 174 may be atleast partially powered by exhaust turbine 176 via a shaft 180 when theboosting device is configured as a turbocharger. However, in otherexamples, such as when engine 10 is provided with a supercharger,compressor 174 may be powered by mechanical input from a motor or theengine and exhaust turbine 176 may be optionally omitted. In still otherexamples, engine 10 may be provided with an electric supercharger (e.g.,an “eBooster”), and compressor 174 may be driven by an electric motor.In still other examples, engine 10 may not be provided with a boostingdevice, such as when engine 10 is a naturally aspirated engine.

A throttle 162 including a throttle plate 164 may be provided in theengine intake passages for varying a flow rate and/or pressure of intakeair provided to the engine cylinders. For example, throttle 162 may bepositioned downstream of compressor 174, as shown in FIG. 1, or may bealternatively provided upstream of compressor 174. A position ofthrottle 162 may be communicated to controller 12 via a signal TP from athrottle position sensor.

An exhaust manifold 148 can receive exhaust gases from other cylindersof engine 10 in addition to cylinder 14. An exhaust gas sensor 126 isshown coupled to exhaust manifold 148 upstream of an emission controldevice 178. Exhaust gas sensor 126 may be selected from among varioussuitable sensors for providing an indication of an exhaust gas air/fuelratio (AFR), such as a linear oxygen sensor or UEGO (universal orwide-range exhaust gas oxygen), a two-state oxygen sensor or EGO, a HEGO(heated EGO), a NOx, a HC, or a CO sensor, for example. In the exampleof FIG. 1, exhaust gas sensor 126 is a UEGO sensor. Emission controldevice 178 may be a three-way catalyst, a NOx trap, various otheremission control devices, or combinations thereof. In the example ofFIG. 1, emission control device 178 is a three-way catalyst.

Each cylinder of engine 10 may include one or more intake valves and oneor more exhaust valves. For example, cylinder 14 is shown including atleast one intake poppet valve 150 and at least one exhaust poppet valve156 located at an upper region of cylinder 14. In some examples, eachcylinder of engine 10, including cylinder 14, may include at least twointake poppet valves and at least two exhaust poppet valves located atan upper region of the cylinder. In this example, intake valve 150 maybe controlled by controller 12 by cam actuation via cam actuation system152, including one or more cams 151. Similarly, exhaust valve 156 may becontrolled by controller 12 via cam actuation system 154, including oneor more cams 153. The position of intake valve 150 and exhaust valve 156may be determined by valve position sensors (not shown) and/or camshaftposition sensors 155 and 157, respectively. In other examples, camshaftposition sensors 155 and 157 may be omitted, as further described withrespect to FIGS. 9 and 10.

During some conditions, controller 12 may vary the signals provided tocam actuation systems 152 and 154 to control the opening and closing ofthe respective intake and exhaust valves. The intake and exhaust valvetiming may be controlled concurrently, or any of a possibility ofvariable intake cam timing, variable exhaust cam timing, dualindependent variable cam timing, or fixed cam timing may be used. Eachcam actuation system may include one or more cams and may utilize one ormore of variable displacement engine (VDE), cam profile switching (CPS),variable cam timing (VCT), variable valve timing (VVT), and/or variablevalve lift (VVL) systems that may be operated by controller 12 to varyvalve operation. In alternative embodiments, intake valve 150 and/orexhaust valve 156 may be controlled by electric valve actuation. Forexample, cylinder 14 may alternatively include an intake valvecontrolled via electric valve actuation and an exhaust valve controlledvia cam actuation, including CPS and/or VCT systems. In other examples,the intake and exhaust valves may be controlled by a common valveactuator (or actuation system) or a variable valve timing actuator (oractuation system).

As further described herein, intake valve 150 and exhaust valve 156 maybe deactivated during VDE mode via electrically actuated rocker armmechanisms. Examples of such systems will be described with respect toFIGS. 2A-2D. In another example, intake valve 150 and exhaust valve 156may be deactivated via a CPS mechanism in which a cam lobe with no liftis used for deactivated valves. Still other valve deactivationmechanisms may also be used, such as for electrically actuated valves.In one embodiment, deactivation of intake valve 150 may be controlled bya first VDE actuator (e.g., a first electrically actuated rocker armmechanism, coupled to intake valve 150) while deactivation of exhaustvalve 156 may be controlled by a second VDE actuator (e.g., a secondelectrically actuated rocker arm mechanism, coupled to exhaust valve156). In alternate embodiments, a single VDE actuator may controldeactivation of both intake and exhaust valves of the cylinder. In stillother embodiments, a single cylinder valve actuator deactivates aplurality of cylinders (both intake and exhaust valves), such as all ofthe cylinders in an engine bank, or a distinct actuator may controldeactivation for all of the intake valves while another distinctactuator controls deactivation for all of the exhaust valves of thedeactivated cylinders. It will be appreciated that if the cylinder is anon-deactivatable cylinder of the VDE engine, then the cylinder may nothave any valve deactivating actuators.

Cylinder 14 can have a compression ratio, which is a ratio of volumeswhen piston 138 is at bottom dead center (BDC) to top dead center (TDC).In one example, the compression ratio is in the range of 9:1 to 10:1.However, in some examples where different fuels are used, thecompression ratio may be increased. This may happen, for example, whenhigher octane fuels or fuels with a higher latent enthalpy ofvaporization are used. The compression ratio may also be increased ifdirect injection is used due to its effect on engine knock.

Each cylinder of engine 10 may include a spark plug 192 for initiatingcombustion. An ignition system 190 can provide an ignition spark tocombustion chamber 14 via spark plug 192 in response to a spark advancesignal SA from controller 12, under select operating modes. A timing ofsignal SA may be adjusted based on engine operating conditions anddriver torque demand. For example, spark may be provided at maximumbrake torque (MBT) timing to maximize engine power and efficiency.Controller 12 may input engine operating conditions, including enginespeed, engine load, and exhaust gas AFR, into a look-up table and outputthe corresponding MBT timing for the input engine operating conditions.In other examples, spark may be retarded from MBT, such as to expeditecatalyst warm-up during engine start or to reduce an occurrence ofengine knock.

In some examples, each cylinder of engine 10 may be configured with oneor more fuel injectors for providing fuel thereto. As a non-limitingexample, cylinder 14 is shown including a fuel injector 166. Fuelinjector 166 may be configured to deliver fuel received from a fuelsystem 8. Fuel system 8 may include one or more fuel tanks, fuel pumps,and fuel rails. Fuel injector 166 is shown coupled directly to cylinder14 for injecting fuel directly therein in proportion to a pulse width ofa signal FPW received from controller 12 via an electronic driver 168.In this manner, fuel injector 166 provides what is known as directinjection (hereafter also referred to as “DI”) of fuel into cylinder 14.While FIG. 1 shows fuel injector 166 positioned to one side of cylinder14, fuel injector 166 may alternatively be located overhead of thepiston, such as near the position of spark plug 192. Such a position mayincrease mixing and combustion when operating the engine with analcohol-based fuel due to the lower volatility of some alcohol-basedfuels. Alternatively, the injector may be located overhead and near theintake valve to increase mixing. Fuel may be delivered to fuel injector166 from a fuel tank of fuel system 8 via a high pressure fuel pump anda fuel rail. Further, the fuel tank may have a pressure transducerproviding a signal to controller 12.

In an alternative example, fuel injector 166 may be arranged in anintake passage rather than coupled directly to cylinder 14 in aconfiguration that provides what is known as port injection of fuel(hereafter also referred to as “PFI”) into an intake port upstream ofcylinder 14. In yet other examples, cylinder 14 may include multipleinjectors, which may be configured as direct fuel injectors, port fuelinjectors, or a combination thereof. As such, it should be appreciatedthat the fuel systems described herein should not be limited by theparticular fuel injector configurations described herein by way ofexample.

Fuel injector 166 may be configured to receive different fuels from fuelsystem 8 in varying relative amounts as a fuel mixture and furtherconfigured to inject this fuel mixture directly into cylinder. Further,fuel may be delivered to cylinder 14 during different strokes of asingle cycle of the cylinder. For example, directly injected fuel may bedelivered at least partially during a previous exhaust stroke, during anintake stroke, and/or during a compression stroke. As such, for a singlecombustion event, one or multiple injections of fuel may be performedper cycle. The multiple injections may be performed during thecompression stroke, intake stroke, or any appropriate combinationthereof in what is referred to as split fuel injection.

Fuel tanks in fuel system 8 may hold fuels of different fuel types, suchas fuels with different fuel qualities and different fuel compositions.The differences may include different alcohol content, different watercontent, different octane, different heats of vaporization, differentfuel blends, and/or combinations thereof, etc. One example of fuels withdifferent heats of vaporization includes gasoline as a first fuel typewith a lower heat of vaporization and ethanol as a second fuel type witha greater heat of vaporization. In another example, the engine may usegasoline as a first fuel type and an alcohol-containing fuel blend, suchas E85 (which is approximately 85% ethanol and 15% gasoline) or M85(which is approximately 85% methanol and 15% gasoline), as a second fueltype. Other feasible substances include water, methanol, a mixture ofalcohol and water, a mixture of water and methanol, a mixture ofalcohols, etc. In still another example, both fuels may be alcoholblends with varying alcohol compositions, wherein the first fuel typemay be a gasoline alcohol blend with a lower concentration of alcohol,such as E10) (which is approximately 10% ethanol), while the second fueltype may be a gasoline alcohol blend with a greater concentration ofalcohol, such as E85 (which is approximately 85% ethanol). Additionally,the first and second fuels may also differ in other fuel qualities, suchas a difference in temperature, viscosity, octane number, etc. Moreover,fuel characteristics of one or both fuel tanks may vary frequently, forexample, due to day to day variations in tank refilling.

Controller 12 is shown in FIG. 1 as a microcomputer, including amicroprocessor unit 106, input/output ports 108, an electronic storagemedium for executable programs (e.g., executable instructions) andcalibration values shown as non-transitory read-only memory chip 110 inthis particular example, random access memory 112, keep alive memory114, and a data bus. Controller 12 may receive various signals fromsensors coupled to engine 10, including signals previously discussed andadditionally including a measurement of inducted mass air flow (MAF)from a mass air flow sensor 122; an engine coolant temperature (ECT)from a temperature sensor 116 coupled to a cooling sleeve 118; anexhaust gas temperature from a temperature sensor 158 coupled to exhaustpassage 135; a profile ignition pickup signal (PIP) from a Hall effectsensor 120 (or other type) coupled to crankshaft 140; throttle position(TP) from a throttle position sensor; signal UEGO from exhaust gassensor 126, which may be used by controller 12 to determine the AFR ofthe exhaust gas; and an absolute manifold pressure signal (MAP) from aMAP sensor 124. An engine speed signal, RPM, may be generated bycontroller 12 from signal PIP. The manifold pressure signal MAP from MAPsensor 124 may be used to provide an indication of vacuum or pressure inthe intake manifold. Controller 12 may infer an engine temperature basedon the engine coolant temperature and infer a temperature of emissioncontrol device 178 based on the signal received from temperature sensor158.

Hall effect sensor 120 may be configured as a crankshaft positionsensor. For example, Hall effect sensor 120 may be configured to monitora toothwheel having teeth placed at equal angle increments, such as 6degrees, that rotates with crankshaft 140. Each time a tooth passes, thevoltage output of Hall effect sensor 120 may switch from near zerovoltage (off) to maximum voltage (on) in a square wave, as illustratedwith respect to FIG. 8. The output of Hall effect sensor 120 enablescontroller 12 to determine the relative angle of crankshaft 140 as itturns. Typically, there are one or more missing teeth at a definedlocation on the toothwheel. The missing teeth may align with a specificcrankshaft position, such as cylinder 1 top dead center (TDC). After themissing teeth have passed Hall effect sensor 120 for a first time duringan engine starting event, an absolute position of crankshaft 140 may beknown. Prior to that time, controller 12 is able to detect changes inposition and crankshaft speed based on the output of Hall effect sensor120, but is unable to determine the absolute position of the crankshaft.The orientation of the crankshaft prior to starting the engine can vary,and therefore the angular rotation of the crankshaft prior to theobservation of the missing teeth also varies.

Controller 12 receives signals from the various sensors of FIG. 1 andemploys the various actuators of FIG. 1 to adjust engine operation basedon the received signals and instructions stored on a memory of thecontroller. For example, the controller may transition the engine tooperating in VDE mode by actuating valve actuators 152 and 154 todeactivate selected cylinders, as further described with respect to FIG.5.

As described above, FIG. 1 shows only one cylinder of a multi-cylinderengine. As such, each cylinder may similarly include its own set ofintake/exhaust valves, fuel injector(s), spark plug, etc. It will beappreciated that engine 10 may include any suitable number of cylinders,including 2, 3, 4, 5, 6, 8, 10, 12, or more cylinders. Further, each ofthese cylinders can include some or all of the various componentsdescribed and depicted by FIG. 1 with reference to cylinder 14.

During selected conditions, such as when the full torque capability ofengine 10 is not requested, one of a first or a second cylinder groupmay be selected for deactivation by controller 12 (herein also referredto as a VDE mode of operation). During the VDE mode, cylinders of theselected group of cylinders may be deactivated by shutting offrespective fuel injectors 166 and deactivating respective intake andexhaust valves 150 and 156. While fuel injectors of the disabledcylinders are turned off, the remaining enabled cylinders continue tocarry out combustion, with corresponding fuel injectors and intake andexhaust valves active and operating. To meet overall engine torquerequirements, the engine produces a greater amount of torque in each ofthe remaining active cylinders than was produced with all of thecylinders carrying out combustion. This requires higher manifoldpressures, resulting in lowered pumping losses and increased engineefficiency. Additionally, the lower effective surface area (from onlythe active cylinders) exposed to combustion reduces engine heat losses,increasing the thermal efficiency of the engine.

Turning now to FIGS. 2A-2D, a partial, cutaway side view of a valvetrain200 is shown. Valvetrain 200 may control intake and exhaust valveoperation in an engine, such as engine 10 of FIG. 1. As such, likecomponents of FIG. 1 and FIGS. 2A-2D are numbered the same and may notbe reintroduced. Specifically, the view shown in FIGS. 2A-2D depicts anelectric latch (herein also referred to as “e-latch”) rocker armmechanism 202 included in valvetrain 200 for operating and deactivatingintake valve 150 of one cylinder of an engine. While valvetrain 200 willbe described with respect to operating intake valve 150, the descriptionis not limited to operating intake valve 150. For example, exhaust valve156 of FIG. 1 and any other engine intake and/or exhaust valves may beoperated similarly.

E-latch rocker arm mechanism 202 conveys radial information from a lobeof cam 151 into linear motion of intake valve 150. For example, based ona lift profile of cam 151, e-latch rocker arm mechanism 202 lifts intakevalve 150 from a valve seat 230 to selectively open and close an intakeport 236 of combustion chamber 14 defined in a cylinder head 240.E-latch rocker arm mechanism 202 includes an inner arm 204 and an outerarm 206. A cam follower 208 may be mounted to inner arm 204 via bearingsand a rocker arm shaft 210. Cam follower 208 is configured to engage cam151 as it is rotated by a camshaft 201. Cam follower 208 is shown as aroller follower (such as a switching roller finger follower, SRFF), butmay alternatively be any other type of cam follower, such as a slider.Cam 151 includes a base circle 151 a (shaded region), and a lobe 151 b(unshaded region), in which a radius between the circumference of cam151 and the center of camshaft 201 is variable and greater than that ofbase circle 151 a. When cam follower 208 is engaged with cam 151 on basecircle 151 a, intake valve 150 is closed (e.g., not lifted). When camfollower 208 is engaged with cam 151 on lobe 151 b, intake valve 150 islifted from valve seat 230, as further described below. A position onlobe 151 b is referred to as lift herein.

A latch pin 214 mounted in outer arm 206 may engage a lip 218 of innerarm 204, after which inner arm 204 and outer arm 206 are constrained tomove in concert. A valve lash adjuster 220 may engage outer arm 206 andprovide a fulcrum on which inner arm 204 and outer arm 206 pivottogether as a unit when latch pin 214 is engaged. Latch pin 214 istranslatable between an engaged position (also referred to as an activeor latched position), as shown in FIGS. 2A and 2C, and a disengagedposition (also referred to as a deactivated or unlatched position), asshown in FIGS. 2B and 2D. In the disengaged position, latch pin 214 nolonger engages (e.g., contacts) lip 218 of inner arm 204, therebydisengaging inner arm 204 from outer arm 206. When latch pin 214 is inthe engaged position, intake valve 150 may be considered to be in anoperational (e.g., active) state. When latch pin 214 is in thedisengaged position, intake valve 150 may be considered to bedeactivated, as further described below. Latch pin 214 may be switchedbetween the engaged (latched) and the disengaged (unlatched) positionsvia actuation of a solenoid 216. Solenoid 216 may be an electromagneticsolenoid actuator having a coil that can generate a magnetic force whenenergized by current. Furthermore, latch pin 214 may be comprised of amagnetic material that is movable via magnetic field changes. Forexample, the latch pin may be at least partially comprised of iron. Assuch, latch pin 214 and solenoid 216 may be considered to be part of acylinder valve deactivation mechanism 252.

In the example of FIGS. 2A-2D, the latching mechanism is bi-stable suchthat no holding current is needed to maintain latch pin 214 in eitherthe engaged or disengaged position. For example, controller 12 mayprovide a short voltage pulse of a first polarity to energize solenoid216 to move latch pin 214 from the engaged position (shown in FIG. 2A)to the disengaged position (shown in FIG. 2B). This action may also bereferred to as unlatching the latch pin. Latch pin 214 may be held inthe disengaged position by an integrated permanent magnet. Similarly, ashort voltage pulse of second polarity, opposite of the first polarity,may be applied to energize solenoid 216 to move latch pin 214 from thedisengaged position (shown in FIG. 2B) to the engaged position (shown inFIG. 2A), where latch pin 214 may be held by a different integratedpermanent magnet. This action may also be referred to as latching thelatch pin. In some examples, one or more travel stops may be included toprevent latch pin 214 from moving beyond the disengaged position and/orthe engaged position.

For example, when solenoid 216 is energized, solenoid current begins torise as the solenoid circuit inductance creates a magnetic force to movelatch pin 214. The magnetic force produced is proportional to

$\left( \frac{I}{} \right)^{2},$

where I is the current to the coil and g is an air gap between latch pin214 and a magnet. As a velocity of latch pin 214 increases, a back(e.g., counter) electromotive force (EMF) is created in the solenoidcircuit. The back EMF produces voltage that is opposite the appliedvoltage and is proportional to the velocity of latch pin 214. As aresult, the current on the solenoid circuit decreases as latch pin 214moves. Once latch pin 214 reaches the end of its travel, the motionceases, as does the back EMF, resulting in a “valley” (e.g., localminimum) in the solenoid current signal. In some examples, a permanentmagnet may be added to generate flux to hold latch pin 214 after itmoves to the magnet. Due to the back EMF from the latch pin movementcausing the solenoid current to decrease, termed an inductive signature,movement of latch pin 214 may be inferred based on the inductivesignature (also referred to herein as an electric current signature) ofsolenoid 216 during the actuation.

In alternative examples, the latching mechanism may be mono-stable, inwhich latch pin 214 may be held in the engaged position by one or moresprings and in the disengaged position by an integrated permanentmagnet. For example, latch pin 214 may be moved to the disengagedposition by supplying a higher current to solenoid 216, after which thecurrent may be reduced to a holding current. Latch pin 214 may then bereturned to the engaged position via one or more springs byde-energizing solenoid 216. As described further herein, movement oflatch pin 214 between the engaged position and the disengaged positionmay be restricted to when cam 151 is on base circle (as shown in FIGS.2A and 2B).

As shown in FIG. 2C, while latch pin 214 is engaged with lip 218 and cam151 rises off of base circle 151 a onto lobe 151 b, outer arm 206 pivotsagainst valve lash adjuster 220 while inner arm 204 presses down onvalve stem 234 via an elephant's foot 224, compressing a valve spring226 against cylinder head 240. As a result, intake valve 150 is liftedoff of valve seat 230. A valve lift profile is determined by the shapeof cam 151 (such as a shape of lobe 151 b) and is a function of anangular position of camshaft 201. When cam 151 returns to base circle151 a, valve spring 226 pushes valve stem 234 against elephant's foot224, causing inner arm 204 to raise, outer arm 206 to raise, and intakevalve 150 to close, as shown in FIG. 2A.

In contrast, when latch pin 214 is disengaged from lip 218 and cam 151rises off of base circle 151 a onto lobe 151 b, cam 151 drives inner arm204 downward via cam follower 208, as shown in FIG. 2D. For example, cam151 may be at or near the maximum lift position. Instead of compressingvalve spring 226, inner arm 204 pivots on a shaft 222 while outer arm206 remains stationary, decoupled from inner arm 204 and cam follower208. Intake valve 150 remains against valve seat 230, and intake port236 of cylinder 14 remains closed. When cam 151 returns to base circle151 a, inner arm 204 may pivot back to its starting position (e.g., theposition shown in FIG. 2B) via a lost motion spring or springs (notshown). The lost motion springs may be coil springs, torsion springs, orany suitable device to ensure the inner arm returns to a position wherelip 218 is above the edge of latch pin 214 so that the latch pin isclear to move to the latched position. By actuating latch pin 214 to thedisengaged position, intake valve 150 is deactivated even while cam 151is on lobe 151 b and has lift.

FIGS. 2A-2D show example configurations with relative positioning of thevarious components. If shown directly contacting each other, or directlycoupled, then such elements may be referred to as directly contacting ordirectly coupled, respectively, at least in one example. Similarly,elements shown contiguous or adjacent to one another may be contiguousor adjacent to each other, respectively, at least in one example. As anexample, components laying in face-sharing contact with each other maybe referred to as in face-sharing contact. As another example, elementspositioned apart from each other with only a space there-between and noother components may be referred to as such, in at least one example. Asyet another example, elements shown above/below one another, at oppositesides to one another, or to the left/right of one another may bereferred to as such, relative to one another. Further, as shown in thefigures, a topmost element or point of element may be referred to as a“top” of the component and a bottommost element or point of the elementmay be referred to as a “bottom” of the component, in at least oneexample. As used herein, top/bottom, upper/lower, above/below, may berelative to a vertical axis of the figures and used to describepositioning of elements of the figures relative to one another. As such,elements shown above other elements are positioned vertically above theother elements, in one example. As yet another example, shapes of theelements depicted within the figures may be referred to as having thoseshapes (e.g., such as being circular, straight, planar, curved, rounded,chamfered, angled, or the like). Further, elements shown intersectingone another may be referred to as intersecting elements or intersectingone another, in at least one example. Further still, an element shownwithin another element or shown outside of another element may bereferred as such, in one example.

Turning to FIG. 3, table 300 depicts a relationship between cam timing,latch pin position, valve state, and an ability of the latch pin tomove. The relationship depicted at table 300 may be leveraged by anengine controller to accurately and reliably diagnose a cylinder valvedeactivation mechanism.

As indicated at 302-304, when the cam position is at base circle (e.g.,base circle 151 a, as shown in FIGS. 2A-2B), that is, when the cam isrotated such that a corresponding cam follower (e.g., cam follower 208of FIGS. 2A-2D) is engaged with the base circle of the cam, the latchpin is moveable. That is, if the latch pin is actuated by energizing acorresponding solenoid, the latch pin can be latched into an engagedposition (row 302) or unlatched into a disengaged position (row 304).When the latch pin is engaged, the corresponding cylinder valve isactive, and the valve will induct air through the cylinder when lifted.As a result, the corresponding cylinder is active, and if all of theengine cylinders are active, the engine is in a non-VDE mode. Incomparison, when the latch pin is disengaged, the corresponding cylindervalve is deactivated, and the valve will remain closed and will notinduct air through the cylinder. As a result, the corresponding cylinderis deactivated, and the engine is in a VDE mode. As elaborated withreference to FIGS. 4-7 and 9-10, an engine controller may monitor forlatch pin movement while the latch pin is latched or unlatched (e.g.,actuated between the engaged and disengaged positions). The latch pinmovement may be inferred based on an electric current signature of theassociated solenoid. If latch pin movement is not detected when thelatch pin is actuated while the cam is at the base circle position, itmay be inferred that the cylinder valve deactivation mechanism isdegraded. In particular, it may be inferred that the latch pin did notmove due to a temporary malfunction such as a hydraulic lash adjusterthat has pumped up, preventing an unlatched pin from re-engaging theinner arm, or a permanent malfunction such as a latch pin that hasseized due to contamination between the outer arm (e.g., a pin bore ofthe outer arm) and the latch pin.

As indicated at 306-308, when the cam position is at a lobe position(e.g., lobe 151 b, as shown in FIGS. 2C-2D), that is, when the camfollower is engaged with the cam off of base circle, the latch pin isnot moveable. That is, if the latch pin is actuated by energizing thecorresponding solenoid while in the engaged position, the latch pincannot be unlatched into a disengaged position because the load from theinner arm on the latch pin creates friction that cannot be overcome bythe force of the solenoid (row 306). Likewise, if the latch pin isactuated by energizing the corresponding solenoid while in thedisengaged position, the latch pin cannot be latched into the engagedposition because the pin will be stopped by the lip of the inner armhitting the tip of the latch pin (row 308). When the latch pin isengaged, the corresponding cylinder valve is active, and the valve willinduct air through the cylinder. As a result, the corresponding cylinderis active, and if all of the engine cylinders are active, the engine isin a non-VDE mode. In comparison, when the latch pin is disengaged, thecorresponding cylinder valve is deactivated, and the valve will notinduct air through the cylinder. As a result, the corresponding cylinderis deactivated, and the engine is in a VDE mode. As elaborated withreference to FIGS. 4-7 and 9-10, an engine controller may monitor forlatch pin movement while the latch pin is engaged or disengaged. Thelatch pin movement may be inferred based on an electric currentsignature of the associated solenoid. If latch pin movement is detectedwhen the corresponding solenoid is energized while the cam is at thelobe position, it may be inferred that the cylinder valve deactivationmechanism is degraded. In particular, it may be inferred that the latchpin moved due to a collapsed lifter (e.g., low oil pressure) or a worncam lobe. In one example, it may be inferred that the latch pin moveddue to the cam remaining at the base circle position even when it wasexpected to be at the lobe position due to the cam lobe being worn.

Next, FIG. 4 shows an example method 400 for controlling operation of aVDE engine, such as engine 10 shown in FIG. 1, that includes the valvedeactivation mechanism shown in FIGS. 2A-2D (e.g., valve deactivationmechanism 252). In particular, cylinder intake and exhaust valves may beput into a desired state (e.g., active or deactivated) during a startingoperation of the engine, even if camshaft position is unknown and/or acurrent valve state is unknown, and during engine shutdown. Differentstarting and shutdown valve modes may facilitate engine spin up and spindown, respectively, such as by minimizing a cylinder air spring.Instructions for carrying out method 400 and the rest of the methodsincluded herein may be executed by a controller (e.g., controller 12 ofFIG. 1) based on instructions stored on the memory of the controller andin conjunction with signals received from sensors of the engine system,such as the sensors described above with reference to FIG. 1. Thecontroller may employ engine actuators of the engine system, such as ane-latch rocker arm solenoid (e.g., solenoid 216 of FIGS. 2A-2D), toadjust engine operation according to the methods described below.

Method 400 begins at 402 and includes estimating and/or measuring engineoperating conditions. The engine operating conditions may include, forexample, engine speed, engine load, torque demand, engine temperature,exhaust temperature, air-fuel ratio, MAP, MAF, ambient conditions (suchas ambient temperature, pressure, and humidity, etc.), a state of theengine, and an ignition state of the vehicle. The state of the enginemay refer to whether the engine is on (e.g., operating at a non-zerospeed, with combustion occurring within engine cylinders), off (e.g., atrest, without combustion occurring in the engine cylinders), or spunelectrically (e.g., via torque from an electric motor, withoutcombustion occurring in the engine cylinders. The ignition state of thevehicle may refer to a position of an ignition switch. As an example,the ignition switch may be in an “off” position, indicating that thevehicle is off (e.g., powered down, with a vehicle speed of zero), or inan “on” position, in which the vehicle is on (e.g., with power suppliedto vehicle systems). The state of the engine and the state of thevehicle may be different. For example, the vehicle may be on andoperating in an electric-only mode, in which an electric machinesupplies torque to propel the vehicle and the engine is off and does notsupply torque to propel the vehicle. As another example, the vehicle maybe on with the engine shut off during an idle-stop. In one example, thevehicle may be at rest when the idle-stop is performed. In anotherexample, the vehicle may be in motion (e.g., coasting) when theidle-stop is performed.

At 404, it is determined if an engine start is requested. For example,an engine start may be requested by a vehicle operator switching theignition switch to an “on” position, such as by turning the ignitionkey, depressing an ignition button, or requesting an engine start from aremote device (such as a key-fob, smartphone, a tablet, etc.). Inanother example, an engine start may be requested by the controller totransition the vehicle from the electric-only mode to an engine mode inwhich combustion occurs in the engine and the vehicle is propelled atleast partially by engine-derived torque. For example, the vehicle maybe transitioned to the engine mode when a state of charge (SOC) of asystem battery (e.g., system battery 58 of FIG. 1) drops below athreshold SOC. The threshold SOC may be a positive, non-zero battery SOClevel below which the system battery may not be able to support orexecute additional vehicle functions while propelling the vehicle viatorque derived from the electric machine (e.g., 3010). As anotherexample, the vehicle may be transitioned to the engine mode if torquedemand rises above a threshold torque. The threshold torque may be apositive, non-zero amount of torque that cannot be met or sustained bythe electric machine alone, for example. In still another example, theengine start may be requested by the vehicle controller to exit anidle-stop.

If an engine start is not requested, method 400 proceeds to 406 todetermine if the engine is on (e.g., operating at a non-zero speed, withcombustion occurring within one or more engine cylinders). If the engineis on, method 400 proceeds to 420, which will be described below. If theengine is not on (e.g., the engine is off), method 400 proceeds to 408and includes maintaining the engine off. Following 408, method 400 ends.

If an engine start is requested at 404, method 400 proceeds to 410 andincludes determining a desired intake valve starting state (e.g., ofintake valve 150 of FIG. 1) and a desired exhaust valve starting state(e.g., of exhaust valve 156 of FIG. 1). The desired starting state ofthe intake valves and the exhaust valves may vary based on engineoperating conditions, such as based on the engine temperature (e.g.,whether the requested engine start is a warm start or a cold start), andmay be different for the intake valves and the exhaust valves. Forexample, when the engine is warm (e.g., above a threshold temperature,the threshold temperature corresponding to a steady-state operatingtemperature), it may be desirable to avoid pumping air into a (warm)downstream catalyst (e.g., emission control device 178 of FIG. 1).Therefore, if it is desirable to spin the engine without pumping air,such as when the engine is warm, the desired starting state of theintake and exhaust valves may be deactivated. In another example, thedesired starting state of the intake valves may be deactivated while thedesired starting state of the exhaust valves may be active. Both ofthese examples will result in zero net airflow through the engine, butwith a different torque signature. That is, deactivated intake valveswith functioning exhaust valves will result in more net pumping lossesand one air spring event per cylinder per engine cycle. Deactivatingboth the intake valve and the exhaust valve will result in two airspring events per engine cycle, but will have lower net pumping losses.In contrast, when the engine is cold, in one example, the desiredstarting state of both the intake and exhaust valves may be active. Instill other examples, the desired starting state of the intake valvesand the desired starting state of the exhaust valves may vary on acylinder-by-cylinder basis. For example, when starting the engine in areduced torque setting is desired, the desired starting state of theintake and exhaust valves of a subset of the cylinders may bedeactivated (or desired starting state of just the intake valves may bedeactivated) while the desired starting state of the intake and exhaustvalves of a remaining number of cylinders may be active. Furthermore, adesired valve state during an engine shutdown may be different than thedesired state for the engine start, as further described below, so thevalves may be in a different state than the desired starting state whenthe engine start is requested.

At 412, method 400 includes energizing an e-latch solenoid of each valvewith voltage of appropriate polarity to place each valve in the desiredstate (as determined at 410). For example, if the desired starting stateis deactivated, the controller may energize the e-latch solenoidincluded in an e-latch rocker arm mechanism of the corresponding valvewith a voltage pulse having a first polarity. As described with respectto FIGS. 2A-2D, the energization of the solenoid with the voltage pulseof the first polarity moves a latch pin coupling an outer arm of thee-latch rocker arm mechanism to an inner arm of the e-latch rocker armmechanism (e.g., latch pin 214, outer arm 206, and inner arm 204 ofFIGS. 2A-2D) from an engaged to a disengaged position. In particular,the movement of the latch pin from the engaged position (in which theinner arm and the outer arm pivot in concert to lift the correspondingvalve when an associated cam rises off of base circle onto a lobe) tothe disengaged position (in which the outer arm is no longer coupled tothe inner arm and the corresponding cylinder valve cannot lift)deactivates the corresponding valve. If the latch pin is already in thedisengaged position, then energizing the associated solenoid with thevoltage pulse of the first polarity will not result in further latch pinmovement. As another example, if the desired starting state is active,the controller may energize the e-latch solenoid of the e-latch rockerarm mechanism of the corresponding valve with a voltage pulse having asecond polarity, which is opposite of the first polarity. As describedwith respect to FIGS. 2A-2D, the energization of the solenoid with thevoltage pulse of the second polarity results in the latch pin movingfrom the disengaged to the engaged position. If the latch pin is alreadyin the engaged position, then energizing the associated solenoid withthe voltage pulse of the second polarity will not result in furtherlatch pin movement. As such, the controller may command the desiredvalve state even if the current valve state is unknown.

As described with respect to FIGS. 2A-2D and summarized in the table ofFIG. 3, latch pin movement may only occur during the energization whenthe associated cam is on the base circle. During the starting operationof the engine, a position of each cam during the energization may beunknown. Therefore, the latch pin of any valve with its cam off of thebase circle will not move.

At 414, method 400 includes cranking the engine via an electric motor,such as a starter motor or an electric machine (e.g., electric machine52 of FIG. 1). For example, electric power may be supplied to theelectric motor, with the amount of power supplied corresponding to anamount of electric torque needed to crank the engine to a desired speed.

At 416, method 400 includes re-energizing the e-latch solenoid of eachvalve after a threshold rotation is reached. The threshold rotationcorresponds to a maximum valve duration, such as a value between 200 and280 degrees of crankshaft rotation. After the maximum valve duration,any cams that were previously off of the base circle (e.g., on the camlobe), resulting in no latch pin movement during the energization at 412(e.g., a first energization), will be returned to the base circle.Therefore, any latch pin that is not in the position corresponding tothe desired valve starting state will be moved during there-energization. Re-energizing the e-latch solenoid of each valveincludes sending a second voltage pulse of a same polarity as during thefirst energization. Latch pins that previously moved during the firstenergization will remain in place, as will any latch pins that werealready in the position corresponding to the desired starting stateprior to the first energization. In this way, each valve may be reliablyplaced into its desired starting state in less than one enginerevolution and without any prior knowledge of the cam position or thevalve state. Furthermore, after placing each valve into the desiredstarting state, the current valve state is known.

At 418, method 400 includes determining crankshaft and camshaftpositions, as will be described with respect to FIGS. 9 and 10. Briefly,after each valve state is known, the movement or lack of movement of alatch pin during a subsequent actuation provides information forinferring a stroke of the corresponding cylinder. For example, theintake valve latch pin will not move during the intake stroke, when theassociated intake cam is on the lobe and an intake valve rocker arm isloaded, and the exhaust valve latch pin will not move during the exhauststroke, when the associated exhaust cam is on the lobe and an exhaustvalve rocker arm is loaded. Latch pin movement or lack of movementduring the actuation may be determined based on an inductive signatureof the corresponding e-latch solenoid. The inductive signature refers tothe e-latch solenoid current generated during the energization. If thecam is on the base circle and the associated latch pin moves, themovement causes the current to momentarily decrease (e.g., a slope ofthe current changes), which appears as a valley in a trace of thesolenoid current during the energization, as described with respect toFIGS. 2A-2D illustrated with respect to FIGS. 14-15. In contrast, whenthe cam is on the lobe and the associated latch pin does not move, thesolenoid current will steadily increase without a valley until a maximumcurrent is reached. In this way, the controller may determine whichlatch pins moved and which latch pins did not move based on the presenceor absence of the current decrease in the inductive signature of theassociated solenoid to provide information regarding the cam position.With the crankshaft and camshaft positions determined, fuel and sparkmay be provided in order to initiate combustion within the enginecylinders, with fuel injection and spark provided at timings relative tothe determined crankshaft and camshaft positions.

At 420, method 400 includes transitioning between operating in a non-VDEmode and a VDE mode based on the operating conditions, as will bedescribed with respect to FIG. 5. For example, the controller may make adetermination of whether to operate in the non-VDE mode, in whichcombustion occurs in all cylinders of the engine, or the VDE mode, inwhich a subset of the cylinders are deactivated while combustion occursin remaining cylinders, based on at least a torque demand. For example,the non-VDE mode may be selected when the torque demand is higher, andthe VDE mode may be selected when the torque demand is lower. The enginemay be transitioned between the non-VDE mode and the VDE mode multipletimes over a drive cycle. The transitioning may include selectivelydeactivating (when transitioning to the VDE mode from the non-VDE mode)or reactivating (when transitioning to the non-VDE mode from the VDEmode) cylinder intake and exhaust valves, such as by energizing thee-latch solenoid of the corresponding valve deactivation mechanism tomove the associated latch pin between the engaged and disengagedpositions. The transitioning may also include selectively deactivatingsome cylinders and/or reactivating other cylinders when changing fromone VDE mode to another VDE mode.

At 422, it is determined if an engine shutdown is requested. As oneexample, a shutdown request from the vehicle operator may be confirmedin response to the ignition switch being moved to the “off” position orby the vehicle operator depressing a push-button. As another example,the engine shutdown may be initiated by the controller, such as inresponse to idle-stop conditions being met and without receiving anoperator request to stop the engine. Idle-stop conditions may include,for example, the battery SOC being more than the threshold SOC (e.g., asdefined at 404), a vehicle speed being within a desired range (e.g., nomore than 30 mph), no request for air conditioner operation, a driverrequested torque being less than a predetermined threshold torque, abrake sensor status indicating that a brake pedal has been depressed, anengine speed being below a threshold engine speed, an input shaftrotation number being below a predetermined threshold rotation number,etc. In one example, the vehicle may be at rest when the idle-stopconditions are met. In another example, the vehicle may be in motion(e.g., coasting) when the idle-stop conditions are met. Any or all ofthe idle-stop conditions may be met for an idle-stop condition to beconfirmed. As another example, the controller may initiate an engineshutdown to transition the vehicle to operating in the electric-onlymode, such as when the battery SOC is greater than the threshold and thetorque demand is less than the threshold torque.

If an engine shutdown is not requested, method 400 proceeds to 424 andincludes maintaining the engine on. As such, combustion will continue tooccur in one or more engine cylinders, with the engine operating at anon-zero speed. The method may then exit. If an engine shutdown isrequested, method 400 proceeds to 426 and includes determining a desiredintake valve shutdown state and a desired exhaust valve shutdown state.The desired shutdown state may be the same or different for the intakevalves and the exhaust valves. Furthermore, the desired intake valveshutdown state and the desired exhaust valve shutdown state may varyfrom cylinder to cylinder. As a first example, the desired shutdownstate for both the intake valves and the exhaust valves may be activefor all cylinders (e.g., a conventional engine shutdown). In a secondexample, the desired shutdown state of both the intake and exhaustvalves may be deactivated for all of the cylinders for zero net airflowthrough the engine and fewer air spring events. Deactivation of theintake and exhaust valves of every cylinder during shutdown may reducethe net engine pumping work and friction so that the engine spinslonger, making the engine ready for a subsequent restart. As a thirdexample, the desired shutdown state of the intake valves may bedeactivated while the desired shutdown state of the exhaust valves maybe active for all of the cylinders, which also results in zero netairflow through the engine. As a fourth example, the desired shutdownstate of the intake and exhaust valves of a subset of the cylinders maybe deactivated (or the desired shutdown state of just the intake valvesmay be deactivated) while the desired shutdown state of the intake andexhaust valves of a remaining number of cylinders may be active. Thecontroller may determine the desired intake valve shutdown state and thedesired shutdown state based on operating conditions, such as atemperature of the catalyst and whether a subsequent engine restart isanticipated. As such, the desired shutdown state may vary based on anorigin of the shutdown request (e.g., the vehicle operator or thecontroller). As an example, the controller may input the operatingconditions into one or more look-up tables, maps, or algorithms andoutput the corresponding desired intake and exhaust valve shutdown statefor each cylinder. As another example, the controller may make a logicaldetermination regarding the desired shutdown state of each intake andeach exhaust valve based on logic rules that are a function of theoperating conditions. As an example, the controller may select one ofthe second or third examples to avoid sending oxygen to the catalystduring shutdown when the catalyst temperature is higher. As anotherexample, the controller may select the second example when a subsequentengine restart is anticipated, such as when the engine is being shutdown for an idle stop.

At 428, method 400 includes energizing the e-latch solenoid of eachvalve with voltage of appropriate polarity when the corresponding cam ison base circle to place each valve in its desired shutdown state. Asanother example, only the e-latch solenoids corresponding to valves notalready in their desired shutdown states may be energized. For example,if the desired shutdown state of the exhaust valves is deactivated,active exhaust valves will be deactivated by moving their latch pins tothe disengaged position via energizing the corresponding e-latchsolenoids with a voltage pulse of the first polarity when the associatedcam is on base circle. If the cam position is unknown for any reason,the valves may be re-energized after the threshold rotation is reached,as described above at 416.

At 430, method 400 includes shutting down the engine. For example,shutting down the engine may include disabling fuel delivery and sparkso that combustion no longer occurs within the engine cylinders andallowing the engine to spin to rest. Following 430, method 400 ends.

In this way, intake and exhaust valve activation state may be accuratelyand efficiently controlled via actuation of an e-latch rocker armmechanism. The e-latch rocker arm mechanism enables the valves to bequickly placed into a desired starting state (e.g., active ordeactivated) during an engine start without interaction with a camshaftpositioning system and without knowledge of the current valve state. Thevalves may also be placed into a desired shutdown state during an engineshutdown, which may be different than the desired starting state. Thedesired starting state and the desired shutdown state may facilitateengine spin up and spin down, respectively. Furthermore, the e-latchrocker arm mechanism enables the crankshaft and camshaft positions to bequickly determined as well as the transitioning of the engine betweenVDE and non-VDE modes of operation, increasing fuel economy. In someexamples, such as when the current valve state is known, the controllermay monitor for latch pin movement during each solenoid energization viaan inductive signature of the solenoid, as further described herein.However, monitoring for latch pin movement is not necessary for settingthe valves to the desired state, particularly when the current valvestate is unknown (such as when an engine start is requested) and it istherefore unknown whether latch pin movement is expected or not.

Turning now to FIG. 5, an example method 500 is shown for selectivelydeactivating cylinder valve actuation mechanisms responsive to engineoperating conditions and diagnosing a cylinder valve actuator. Therein,cylinder valves may be selectively deactivated by actuating an electriclatch (e-latch) rocker arm mechanism via energization of an associatedelectric solenoid (herein also referred to as an e-latch solenoid). Thee-latch rocker arm mechanism may then be diagnosed based on latch pinmovement during the actuation. The operating sequence of FIG. 5 may beproduced via the system of FIGS. 1 and 2A-2D.

At 502, the method includes estimating and/or measuring engine operatingconditions such as engine speed, engine load, driver torque demand,boost pressure, MAP, MAF, vehicle speed, engine temperature, ambientconditions (such as ambient temperature, pressure, and humidity), etc.At 504, it may be determined if the estimated engine conditions enableentry of the engine into a VDE mode where the engine can be operatedwith one or more cylinders selectively deactivated. In one example, VDEmode entry conditions may be met if the torque demand, or the vehiclespeed, is below a threshold.

If VDE mode entry conditions are not met, at 506, the method includesmaintaining all engine cylinders active and combusting fuel in all thecylinders. At 508, while operating in a non-VDE mode, the methodincludes opportunistically performing a low speed e-latch mechanismdiagnostic, as elaborated at FIG. 7. Briefly, therein, the e-latchsolenoid may be energized to actively and intrusively move a latch pinof the rocker arm mechanism between an engaged and disengaged position.The e-latch rocker arm mechanism is then diagnosed based on an inductivecurrent signature generated during the energization. Following 508,method 500 ends.

If VDE entry conditions are met, at 510, the method includes selectingcylinders to be deactivated. This includes selecting a total number ofcylinders to deactivate as well as an identity of the cylinders to bedeactivated. In one example, the number of cylinders to be deactivatedmay increase as the driver torque demand decreases. For example, wherean engine has two banks of cylinders, half the total number of enginecylinders may be deactivated by deactivating all cylinders of one bankwhile maintaining all cylinders of the other bank active. Alternatively,an equal number of cylinders may be deactivated from both banks. Asanother example, if the torque demand is lower, more than half of thecylinders may be deactivated, including cylinders from both banks.

In still other examples, the controller may determine a desiredinduction ratio based at least on operator torque demand. The enginecylinder induction ratio is an actual total number of cylinder firingevents divided by an actual total number of cylinder intake strokes. Inone example, the actual total number of cylinder intake strokes is apredetermined number. As used herein, a cylinder activation event refersto a cylinder firing with intake and exhaust valves opening and closingduring a cycle of the cylinder, while a cylinder deactivation eventrefers to a cylinder not firing with intake and exhaust valves heldclosed during a cycle of the cylinder. An engine event may be a strokeof a cylinder occurring (e.g., intake, compression, power, exhaust), anintake or exhaust valve opening or closing time, a time of ignition ofan air-fuel mixture in the cylinder, a position of a piston in thecylinder with respect to the crankshaft position, or otherengine-related event. The engine event number corresponds to aparticular cylinder. For example, engine event number one may correspondto a compression stroke of cylinder number one. Engine event number twomay correspond to a compression stroke of cylinder number three. A cyclenumber refers to an engine cycle, which includes one event (activationor deactivation) in each cylinder. For example, a first cycle iscompleted when each cylinder of an engine has completed all four strokeevents (intake, compression, expansion, and exhaust events), in thefiring order. The second cycle starts when each cylinder of the enginestarts another iteration of all four stroke events. The target ordesired induction ratio may be determined from the operator requestedengine torque. In particular, allowable engine cylinder induction ratiovalues may be stored in a table or function that may be indexed bydesired engine torque and engine speed. Engine cylinder induction ratiovalues that may provide the requested engine torque may be part of agroup of available engine cylinder induction ratio values. Then, theengine cylinder induction ratio that provides the fewest number ofactive engine cylinders during a cycle may be selected from the group ofavailable engine cylinder induction ratio values to provide the desiredengine cylinder induction ratio. In this way, a single desired enginecylinder induction ratio may be selected from a group of a large numberof engine cylinder induction ratio. It will be appreciated that theselected engine cylinder induction ratio may then be provided via one ofa plurality of possible cylinder deactivation patterns.

As one example, a target induction ratio of ½ (or 0.5) implies that forevery 2 cylinder events, one cylinder is active or fired and one isdeactivated or skipped. As another example, a target induction ratio of⅓ (or 0.33) implies that for every 3 cylinder events, one cylinder isactive and the remaining two are deactivated.

The controller may also select a cylinder pattern for deactivation thatprovides the desired induction ratio. As an example, an inductionpattern for an induction ratio of ½ may include every other cylinderbeing selectively deactivated to produce half of the power, on average.Further, the same pattern may be applied for each consecutive enginecycle such that the same cylinders are skipped on consecutive enginecycles while the remaining cylinders are fired on each of the enginecycles. As another example, an induction pattern for an induction ratioof ⅓ may include two out of every three cylinders being selectivelydeactivated to produce a third of the power, on average. Further, theinduction ratio may be provided by different cylinders being skipped oneach engine cycle.

Once the cylinder pattern corresponding to the desired induction ratiois selected, the controller may disable fuel and spark and deactivatecylinder valve mechanisms in accordance with the selected cylinderpattern to provide the target induction ratio. The selective cylinderdeactivation includes, for the selected cylinders to be deactivated,holding the cylinder valves closed, with no fuel injected into thecylinders, for an entire engine cycle of 720 crank angle degrees (thatis, for all four strokes of a cylinder).

It will be appreciated that the decision to activate or deactivate acylinder and open or close the cylinder's intake and exhaust valve maybe made a predetermined number of cylinder events (e.g., one cylinderevent, or alternatively, one cylinder cycle) before the cylinder is tobe activated or deactivated to allow time to begin the process ofopening and closing intake and exhaust valves of the cylinder. Forexample, for an eight cylinder engine with a firing order of1-3-7-2-6-5-4-8, the decision to activate or deactivate cylinder numberseven may be made during an intake or compression stroke of cylindernumber seven one engine cycle before cylinder number seven is activatedor deactivated. Alternatively, the decision to activate or not activatea cylinder may be made a predetermined number of engine events orcylinder events before the selected cylinder is activated ordeactivated. In still further examples, the number of cylinder eventsmay be adjusted based on hardware capabilities and current engineoperating conditions.

At 512, the method includes actuating the e-latch rocker arm mechanismof the selected cylinders to maintain intake and exhaust valves of thosecylinders closed. This includes, at 514, the controller sending a signalto energize the e-latch solenoid coupled to the e-latch rocker armmechanism of the intake and exhaust valves of the selected cylinders.The timing of the signals to the intake and exhaust solenoids areselected to coincide with the associated cam being on base circle. Theenergization of the solenoid results in a change in the position of alatch pin (e.g., latch pin 214 of FIGS. 2A-2D) coupling an outer arm ofthe e-latch rocker arm mechanism to an inner arm of the e-latch rockerarm mechanism (e.g., outer arm 206 and inner arm 204 of FIGS. 2A-2D). Inparticular, energizing the e-latch solenoid with a voltage pulse of afirst polarity moves the latch pin to a disengaged position where theouter arm is no longer coupled to the inner arm and the correspondingcylinder valve cannot lift. As described with respect to FIG. 2D, withthe outer arm disengaged from the inner arm, the outer arm remainsstationary while the inner arm pivots against a shaft instead of liftingthe valve when an associated cam rises off of base circle. At 516, themethod further includes, while transitioning to the VDE mode,opportunistically diagnosing the e-latch rocker arm mechanism based onlatch pin movement during the actuation of the solenoid. As elaboratedat FIG. 6A, the latch pin's motion during the energization of theassociated solenoid is inferred via an inductive signature of currentgenerated during the solenoid energization. By diagnosing the latchpin's motion when entry into the VDE mode has been commanded, the VDEmechanism is diagnosed non-intrusively and without relying on costlysensors. At 518, the method includes disabling fuel and spark to theselected cylinders. Fuel flow and spark to the deactivated cylinders maybe stopped by deactivating cylinder fuel injectors (e.g., fuel injector166 of FIG. 1) and disabling a spark signal commanded to a givencylinder's spark plug (e.g., spark plug 192 of FIG. 1). Alternatively,the method may not disable the spark signal since, even in the presenceof spark, the cylinder will not be able to fire without fuel and air. Asa result, the deactivated cylinders do not combust air and fuel thereinand therefore do not produce any torque. At 520, the method includesadjusting engine operating parameters to maintain torque demand viaremaining cylinders. The remaining active cylinders operate with ahigher average cylinder load in the VDE mode (relative to the non-VDEmode) to meet the driver torque demand, increasing pumping efficiencyand fuel economy of the engine. For example, one or more of airflow,spark timing, and cylinder valve timing may be adjusted in theremaining, active cylinders in order to maintain the engine torquedemand and minimize torque disturbances during the transition tooperating in the VDE mode.

At 522, it may be determined if engine operating conditions have changedto enable exit of the engine from the VDE mode and entry into thenon-VDE mode where the engine can be operated with all cylinders active.In one example, non-VDE mode entry conditions (or VDE mode exitconditions) may be met if the torque demand, or the vehicle speed, isabove a threshold.

If non-VDE mode entry conditions are not met, at 524, the methodincludes maintaining engine operation with one or more cylindersdeactivated and combusting fuel in remaining active cylinders. Else, ifnon-VDE mode entry conditions are met, at 526, the method includesactuating the e-latch rocker arm mechanism of the selected cylinders toenable intake and exhaust valves of previously deactivated cylinders tolift. This includes, at 528, the controller sending a signal to energizethe e-latch solenoid coupled to the e-latch rocker mechanism of thevalves of the deactivated cylinders. The timing of the signals to theintake and exhaust solenoids are selected to coincide with theassociated cam being on base circle. The energization of the solenoidresults in a change in the position of the latch pin. In particular,energizing the e-latch solenoid with a voltage pulse of a secondpolarity, which is opposite of the first polarity, moves the latch pinto an engaged position where the outer arm is coupled to the inner armand valve lift is possible. As described with respect to FIG. 2C, withthe latch pin in the engaged position, the outer arm and inner arm movein concert, pivoting against a valve lash adjuster and lifting the valvebased on a profile of the associated cam. At 530, the method furtherincludes opportunistically diagnosing the e-latch rocker arm mechanismbased on latch pin movement during the actuation of the solenoid. Aselaborated at FIG. 6B, by monitoring the latch pin's motion via theinductive signature during the energization of the associated solenoid,the VDE mechanism can be reliably diagnosed in a non-intrusive manner.In particular, degradation of the e-latch rocker arm mechanism in whichthe latch pin is stuck in the deactivated position may be determined,enabling the controller to adjust engine operation accordingly toaccount for deactivation of the corresponding cylinder. Furthermore, apumped up (e.g., overextended) lifter or worn cam lobe may beidentified.

At 532, the method includes resuming fuel and spark in the previouslydeactivated cylinders. As a result, the reactivated cylinders start tocombust air and fuel therein and therefore start to produce torque. At534, the method includes adjusting engine operating parameters tomaintain the torque demand. At this time, since all cylinders areactive, each active cylinder may operate with a lower average cylinderload relative to the VDE mode to meet the driver torque demand. In someexamples, one or more of airflow, spark timing, and cylinder valvetiming may be adjusted in order to minimize torque disturbances duringthe transition to operating in the non-VDE mode. Additionally, aselaborated with reference to FIGS. 6A-6B, one or more engine operatingparameters may be adjusted based on the outcome of the diagnostic, suchas based on whether any of the cylinder valves are degraded (e.g.,whether they are stuck opening or stuck closed). Following 534, method500 ends.

Turning now to FIGS. 6A and 6B, an example method 600 is depicted fordiagnosing cylinder valve deactivation mechanisms while entering andexiting a cylinder deactivation mode over the course of a drive cycle.The method is non-intrusive and does not require a VDE mode to beenforced. Instead, the method leverages the inherent transition of theengine into and out of the VDE mode over the course of a drive cycle viaan e-latch rocker arm mechanism (e.g., e-latch rocker arm mechanism 202of FIGS. 2A-2D). The method of FIG. 6A may be performed as a part of themethod of FIG. 5, such as at 516, when a VDE mode is entered. Thus, allthe steps of FIG. 6A are performed after cylinder valve deactivation hasbeen commanded. Likewise, the method of FIG. 6B may be performed as apart of the method of FIG. 5, such as at 530, when a non-VDE mode isentered. Thus, all the steps of FIG. 6B are performed after cylindervalve reactivation has been commanded.

At 604, after cylinder valve deactivation has been commanded for aselected cylinder, it is determined if the cam for the selected cylinderis on the base circle. Herein, the cam may be an intake cam or anexhaust cam of the selected cylinder, the intake cam coupled to thedeactivation mechanism of the intake valve and the exhaust cam coupledto the deactivation mechanism of the exhaust valve of the givencylinder. In one example, cam position on the base circle may beinferred based on the output of a camshaft position sensor. In anotherexample, cam position on the base circle may be inferred based oncrankshaft position (e.g., as output by a crankshaft position sensor,such as Hall effect sensor 120 of FIG. 1) and cylinder firing order, asfurther described with respect to FIG. 9. For example, the controllermay infer that the intake cam is on the base circle during thecompression, exhaust, and power strokes, and that the exhaust cam is onthe base circle during the intake, compression, and power strokes. Thecrankshaft positions at which the intake and exhaust cams move off ofbase circle may be further based on cam phasing and a lift profile ofthe corresponding cam. If the cam is not on the base circle, at 618,method 600 includes not actuating the e-latch rocker arm mechanism. Thatis, the controller may wait until the cam has returned to the basecircle to actuate the e-latch rocker arm mechanism, as the valve statemay not be transitioned while the cam is off of the base circle (e.g.,during cam lift).

If the cam is on the base circle while a VDE mode has been commanded, at606, the method includes inferring latch pin movement parameters basedon an inductive signature generated while energizing the e-latchsolenoid to move the latch pin to a disengaged position. For example,latch pin motion may be inferred based on a decrease in the electricalcurrent signature of the solenoid as well as a time corresponding to thedecrease (e.g., valley). For example, as the solenoid is energized (witha voltage pulse having a first polarity), the current increases, causingan increase in a magnetic force on the latch pin until the magneticforce is strong enough to pull the latch pin into the disengagedposition. The movement of the latch pin causes a brief reduction in thecurrent through the solenoid due to a back EMF, after which the currentcontinues to increase to its maximum level. Such an inductive signatureis illustrated with respect to FIG. 12, for example. The controller maylog the crank angle when the latch pin movement happens. For example,the controller may log the angle at which the latch pin transitions fromthe engaged position to the disengaged position. The movement parametersthat are inferred may include, for example, a rate of change in thecurrent, as inferred from a slope of the current (e.g., the derivativeof the current signal). As another example, the inferred parametersinclude a time taken for the latch pin to move from an initial, engagedposition to the final, disengaged position. As another example, theinferred parameters may include a velocity of the latch pin when it hitsthe end stop, as inferred based on a magnitude of the current decrease(e.g., back EMF is proportional to the velocity latch pin). As stillanother example, the inferred parameters include a determination of howhard the latching pin hits the end stop when it reaches the disengagedposition (that is, a relative force with which it hits the end stop), asinferred based on a magnitude of the current decrease. Still otherparameters may be inferred.

At 608, based on the inductive signature generated during the solenoidenergization, and further based on the inferred latch pin movementparameters, it may be determined if latch pin movement was detected. Aselaborated with reference to the table of FIG. 3, in particular at 302and 304, when the cam is at the base circle, the latch pin is movablefor transitioning from an engaged position to a disengaged position todeactivate a cylinder valve. That is, in response to solenoidenergization, latch pin movement is expected. If the inductive signatureindicates that latch pin movement was detected, as was expected, then at610, it may be inferred that the e-latch rocker arm mechanism isfunctional. At 612, the method includes adjusting a current applied tothe e-latch mechanism of the given cylinder during a subsequenttransition into a VDE mode (e.g., when valve deactivation issubsequently commanded for the given cylinder) based on the inferredlatch pin movement parameters. As an example, the engine controller mayadjust a magnitude of the current applied to energize the solenoidduring a subsequent valve deactivation operation based on the inferredtime taken for the latch pin to move to the disengaged position as wellas how hard it hit the end stop. For example, the controller may reducethe current applied to the solenoid to reduce the force with which thelatch pin hits the end stop when entering the disengaged position,thereby reducing pin wear and extending component life. As anotherexample, the controller may use the time taken for the latch pin totransition from the engaged position to the disengaged position tomeasure part-to-part variability, such as the solenoid mechanicalconstruction that has variability in the actual flux path in themagnetic circuit. As still another example, the controller may use thefinal maximum current through the solenoid coil to determine thepart-to-part variability of the solenoid resistance. Further still, thecontroller may increase or decrease the engine speed range whereinswitching is enabled. For example, a degraded connection to the solenoid(e.g., high resistance) would slow down the actuator response. If thecontroller detects that one or more latch pins are moving more slowlythan expected, the controller may reduce the maximum speed that VDE canbe utilized since a slow moving latch pin may not be able to completeits stroke during the shorter base circle event at higher engine speeds.As yet another example, the controller may use the inferred parametersto confirm camshaft dynamics, as elaborated at FIGS. 9 and 10. Following612, method 600 ends.

Returning to 608, if the inductive signature indicates that latch pinmovement was not detected, then at 614, it may be indicated that thee-latch rocker arm mechanism is degraded. In particular, it may beinferred that the latch pin did not move if the brief reduction in thesolenoid current is not observed. Indicating degradation of the e-latchrocker arm mechanism may include setting a diagnostic code, illuminatinga light, and/or or notifying a vehicle occupant via an informationcenter. At 616, responsive to the indication of degradation, the methodincludes disabling deactivation of the given cylinder until e-latchrocker arm repair or replacement is confirmed. Following 616, method 600ends.

Turning now to FIG. 6B, at 630, after cylinder valve reactivation hasbeen commanded for a selected cylinder, it is determined if the cam forthe selected cylinder is on the base circle. Herein, the cam may be anintake cam or an exhaust cam of the selected cylinder, the intake camcoupled to the deactivation mechanism of the intake valve, and theexhaust cam coupled to the deactivation mechanism of the exhaust valveof the given cylinder. As elaborated earlier, cam position on the basecircle may be inferred based on the output of a cam position sensor orbased on measured or sensed cam timing. If the cam is not on the basecircle, at 644, method 600 includes not actuating the e-latch rocker armmechanism. That is, the controller may wait until the cam has returnedto the base circle to actuate the e-latch rocker arm mechanism, as thevalve state may not be transitioned while the cam is off of the basecircle (e.g., during cam lift).

If the cam is on the base circle while a non-VDE mode has beencommanded, at 632, the method includes inferring latch pin movementparameters based on an inductive signature generated while energizingthe e-latch solenoid to move the latch pin to the engaged position. Asdescribed above at 606 of FIG. 6A, the movement of the latch pin causesa brief reduction in the current through the solenoid, after which thecurrent continues to increase to its maximum level. Therefore, themovement of the latch pin from the disengaged to the engaged positioncan be inferred from the brief reduction in solenoid current. Thecontroller may log the crank angle when the latch pin movement happens.For example, the controller may log the angle at which the pintransitions from the disengaged position to the engaged position. Themovement parameters that are inferred may include, for example, a rateof change in the current, as inferred from a slope of the curve in theinductive signature. As another example, the inferred parameters includea time taken for the latch pin to move from an initial position to theengaged position, as inferred based on the time taken to move from thedisengaged position to the engaged position. As another example, theinferred parameters may include a velocity of the latch pin when it hitsthe end stop, as inferred based on a magnitude of the current decrease(e.g., back EMF is proportional to the velocity latch pin). As stillanother example, the inferred parameters include a determination of howhard the latch pin hits the inner arm when it reaches the engagedposition (that is, the force with which it hits the hard-stop in theinner arm), as inferred based on the magnitude of the current dip. Stillother parameters may be inferred.

At 634, based on the inductive signature generated during the solenoidenergization, and further based on the inferred latch pin movementparameters, it may be determined if latch pin movement was detected. Aselaborated with reference to the table of FIG. 3, in particular at 302and 304, when the cam is at the base circle, the latch pin is movablewhen transitioning from a disengaged position to an engaged position toreactivate a cylinder valve. That is, in response to solenoidenergization, latch pin movement is expected. If the inductive signatureindicates that latch pin movement was detected, as was expected, then at636, it may be inferred that the e-latch rocker arm mechanism isfunctional. At 638, the method includes adjusting a current applied tothe latching mechanism of the given cylinder during a subsequenttransition into a non-VDE mode (e.g., when valve reactivation issubsequently commanded for the given cylinder) based on the inferredlatch pin movement parameters. As an example, the engine controller mayadjust a magnitude of the current applied to energize the solenoidduring a subsequent valve reactivation operation based on the inferredtime taken for the latch pin to move to the engaged position as well ashow hard it hit. For example, the controller may reduce the currentapplied to the e-latch solenoid to reduce the force (or the velocity)with which the latch pin hits a hard-stop of an inner arm of the e-latchrocker arm mechanism when entering the engaged position, therebyreducing pin wear and extending component life. As another example, thecontroller may use the time taken for the latch pin to transition fromthe disengaged position to the engaged position to measure part-to-partvariability, such as the solenoid mechanical construction that hasvariability in the actual flux path in the magnetic circuit. As anotherexample, the controller may use the final maximum current through thesolenoid coil to determine the part-to-part variability of the solenoidresistance. Further still, the controller may increase or decrease theengine speed range wherein switching is enabled. For example, if thecontroller detects that one or more latch pins are moving more slowlythan expected, the controller may reduce the maximum speed that VDE canbe utilized since a slow moving latch pin may not be able to completeits stroke during the shorter base circle event at higher engine speeds.As yet another example, the controller may use the inferred parametersto confirm camshaft dynamics. Following 638, method 600 ends.

Returning to 634, if the inductive signature indicates that latch pinmovement was not detected, then at 640, it may be indicated that thee-latch rocker arm mechanism is degraded. In particular, it may beinferred that the latch pin is stuck in the disengaged position.Indicating degradation of the e-latch rocker arm may include setting adiagnostic code, illuminating a light, and/or or notifying a vehicleoccupant via the information center. At 642, responsive to theindication of degradation, the method includes maintaining thecorresponding cylinder deactivated until e-latch rocker arm repair orreplacement is confirmed. As an example, if it is determined that theexhaust valve deactivation mechanism is degraded and the latch pin isstuck in the disengaged position, the controller may maintain the intakevalve deactivated, even if it is not degraded, while the exhaust valveis stuck in the deactivated position and adjust engine operationaccordingly. For example, the average load of all remaining activecylinders may be increased to compensate for the given cylinder beingmaintained deactivated. Following 642, method 600 ends.

In this way, by correlating cylinder valve deactivation with latch pinmovement, VDE diagnostics can be completed while also establishing a camtiming where the movement occurred.

Turning now to FIG. 7, an example method 700 is depicted for diagnosingan e-latch rocker arm mechanism, which serves as a cylinder valvedeactivation mechanism, opportunistically during low speed conditionswhen cylinder deactivation is otherwise not required. At low enginespeeds, there is time to move a latch pin of the e-latch rocker armmechanism (e.g., latch pin 214 of FIGS. 2A-2D) from a first position, toa second position, and back to the first position to confirm theoperation of the e-latch rocker arm mechanism, independent of a desiredvalve operating state (e.g., activated or deactivated). Unlike themethod of FIGS. 6A-6B, method 700 does not require a transition to a VDEmode of operation. However, a large portion of the steps of method 700may overlap with the method of FIGS. 6A-6B.

At 702, the method includes estimating and/or measuring engine operatingconditions. These may include, for example, engine speed, engine load,torque demand, engine temperature, exhaust temperature, MAP, MAF,air-fuel ratio, etc. At 704, the method includes confirming ifconditions have been met for performing the low speed e-latch rocker armmechanism (e.g., VDE mechanism) diagnostic. In one example, low speeddiagnostic conditions may be considered met if the engine is idling. Inanother example, the low speed diagnostic conditions may be consideredmet if the engine is at or below a threshold speed. The threshold speedmay be a positive, non-zero speed value that may be at or near a typicalidle speed. As a non-limiting example, the threshold speed may be 1000RPM. In still another example, the low speed diagnostic conditions aremet when the engine is a green engine that is being started for thefirst time since assembly, such as while still at an assembly plant. Assuch, cylinder valve deactivation is not required at low engine speeds.Thus, by selectively enabling the VDE mechanism diagnostic during lowspeed conditions, the cylinder deactivation mechanism can be diagnosedbefore it is needed at higher engine speed-load conditions of the samedrive cycle. Specifically, the e-latch rocker arm system can beconfirmed prior to using the latching mechanism for valve lift control.In addition, the likelihood of completing the VDE mechanism diagnosticon a given drive cycle is increased by taking advantage of the largeramount of time available for enabling or disabling the VDE mechanism. Iflow speed e-latch rocker arm mechanism diagnostic conditions are notmet, at 706, the method includes not actuating the e-latch rocker armmechanism. For example, an associated solenoid (e.g., solenoid 216 ofFIGS. 2A-2D) will not be energized, as moving the latch pin when the lowspeed diagnostic conditions are not met may result in an inadvertentchange in the operating state of the corresponding valve. The methodexits and the VDE diagnostic is not conducted at this time.

If the low speed e-latch rocker arm mechanism diagnostic conditions aremet, it is determined if the cam is positioned at the beginning of thebase circle for the selected cylinder and valve at 708. Herein, the cammay be an intake cam or an exhaust cam of the selected cylinder, theintake cam coupled to the deactivation mechanism of the intake valve andthe exhaust cam coupled to the deactivation mechanism of the exhaustvalve of the given cylinder. In one example, cam position at thebeginning of the base circle may be inferred based on the output of acamshaft position sensor. In another example, cam position at thebeginning of the base circle may be inferred based on crankshaftposition (e.g., as output by a crankshaft position sensor, such as Halleffect sensor 120 of FIG. 1) and cylinder firing order. For example, thecontroller may infer that the intake cam is at the beginning of the basecircle during the compression stroke, and that the exhaust cam is at thebeginning of the base circle during the intake stroke. The crankshaftpositions at which the intake and exhaust cams reach the beginning ofthe base circle may be further based on cam phasing and a lift profileof the corresponding cam. If the cam is not at the beginning of the basecircle, at 736 it may be determined if the cam is at the beginning ofthe lift profile. In one example, the cam may be inferred to be at thebeginning of the lift profile based on camshaft position sensor outputor cam timing. If the cam is neither at the beginning of the base circlenor at the beginning of the lift profile, the method returns to 704 tocontinue checking the position of the cam so that the method may executeas long as conditions for performing the low speed diagnostic continueto be met.

If the cam is at the beginning of the base circle, at 710, the methodincludes energizing the e-latch solenoid to move the latch pin to adisengaged position. In particular, the e-latch solenoid may beenergized with a voltage pulse of a first polarity. Then at 712, themethod includes inferring latch pin movement parameters based on aninductive signature generated while energizing the e-latch solenoid tomove the latch pin to the disengaged position. The controller may logthe crank angle when the latching pin movement happens. For example, thecontroller may log the angle or time at which the latch pin transitionsfrom the engaged position to the disengaged position based on a briefreduction in current through the solenoid, as elaborated above withrespect to FIG. 6A. The movement parameters that are inferred mayinclude, for example, a rate of change in the current, as inferred froma slope of the current (or the derivative of the current), a time takenfor the latch pin to move from the engaged position to the disengagedposition, as inferred based on the time taken for the current to exhibitthe brief reduction from a start of a voltage pulse supplied to thesolenoid, and a determination of how hard the latch pin hits when itreaches the disengaged position (that is, the force with which it hitsthe end stop), as inferred based on the timing and magnitude of thecurrent decrease. Still other parameters may be inferred, such as thevelocity of the latch pin when it hits the end stop. As an example, thediagnostic may include applying a voltage or duty cycle lower than anormal level for deactivating the rocker arm to test whether the latchpin is able to move even in the presence of a lower actuating force.Successful switching with lower actuating voltage implies a higherlikelihood of successful switching with the normal actuating voltageeven in the presence of other noise factors, such as increased coilresistance due to heating and increase pin friction due to different oilconditions.

At 714, based on the inductive signature generated during the solenoidenergization, and further based on the inferred latch pin movementparameters, it may be determined if latch pin movement was detected. Aselaborated with reference to the table of FIG. 3, when the cam is at thebase circle, the latch pin is movable when transitioning from theengaged position to the disengaged position to deactivate a cylindervalve. That is, in response to solenoid energization, latch pin movementis expected. If the inductive signature indicates that latch pinmovement was not detected, then at 716, it may be indicated that thee-latch rocker arm mechanism is degraded. In particular, it may beinferred that the latch pin did not move from the engaged position tothe disengaged position and is stuck in the engaged position. Indicatingdegradation of the e-latch rocker arm may include setting a diagnosticcode, illuminating a light, and/or or notifying a vehicle occupant viaan information center.

Additionally or alternatively, prior to indicating degradation, thecontroller may first confirm that the latch pin was not already in thedisengaged position when the unlatching was commanded, which would leadto an absence of latch pin movement. To confirm that the latch pin wasnot already in the disengaged position, the controller may re-energizethe solenoid with a voltage pulse of a second polarity, which isopposite of the first polarity, and monitor for latch pin movement. Asdescribed with respect to FIGS. 2A-2D, the voltage pulse of the secondpolarity actuates the latch pin from the disengaged position to theengaged position. Therefore, if latch pin movement is detected inresponse to the voltage pulse of the second polarity, it may be inferredthat the latch pin is now known to be in the engaged position,degradation may not be indicated, and the diagnostic routine may berepeated to verify full latch pin function. Conversely, if latch pinmovement is not detected in response to the voltage pulse of the secondpolarity, e-latch rocker arm mechanism degradation may be confirmed.

At 718, responsive to the indication of degradation, the method includesdisabling deactivation of the given cylinder until e-latch rocker armrepair or replacement is confirmed. That is, the degraded cylinder ismaintained active since the latch pin is stuck in the engaged position.The method then ends.

If the inductive signature indicates that latch pin movement wasdetected at 714, as was expected, then at 720, it may be inferred thatthe e-latch rocker arm mechanism is functional. Next, the method movesto 722 and includes energizing the e-latch solenoid to move the latchpin to the engaged position. For example, since a change in valveoperating state is not desired (e.g., operation in the VDE mode is notdesired), the latch pin may be quickly moved back to the engagedposition before the cam moves off of the base circle. Then at 724, themethod includes inferring latch pin movement parameters based on aninductive signature generated while energizing the e-latch solenoid tomove the latch pin to the engaged position.

At 726, as at 714, based on the inductive signature generated during thesolenoid energization, and further based on the inferred latch pinmovement parameters, it may be determined if latch pin movement wasdetected. As elaborated with reference to the table of FIG. 3, when thecam is at the base circle, the latch pin is movable when transitioningfrom the disengaged position to the engaged position to reactivate thecylinder valve. That is, in response to solenoid energization, latch pinmovement is expected. If the inductive signature indicates that latchpin movement was not detected, then at 728, it may be indicated that thee-latch rocker arm mechanism is degraded. In particular, it may beinferred that the latch pin did not move from the disengaged position tothe engaged position and is stuck in the disengaged position Indicatingdegradation of the e-latch rocker arm may include setting a diagnosticcode, illuminating a light, and/or or notifying a vehicle occupant viathe information center. At 730, responsive to the indication ofdegradation, the method includes maintaining the corresponding cylinderdeactivated until the e-latch rocker arm mechanism is repaired,replaced, or otherwise indicated to be functional. For example, if theexhaust valve deactivation mechanism is determined to be degraded andstuck in the disengaged position, maintaining the exhaust valve in thedeactivated state, the intake valve may be transitioned to thedeactivated state, even if the intake valve deactivation mechanism isfunctional, to maintain the cylinder deactivated. The method then ends.

In some examples, the controller may additionally periodically attemptto latch the rocker arm mechanism by energizing the correspondingsolenoid with a voltage pulse of the second polarity and monitoring forlatch pin movement. For example, latching may be attempted once perdrive cycle or once per a duration of engine operation (such as once perevery 3 hours of engine operation, as one non-limiting example). Iflatch pin movement is detected due to the latch pin moving to theengaged position, the cylinder may be maintained in the active stateuntil the e-latch rocker arm mechanism is repaired.

If the inductive signature indicates that latch pin movement wasdetected, as was expected, then at 732, it may be inferred that thee-latch rocker arm mechanism is functional. Next, at 734, the methodincludes adjusting a current applied to the e-latch mechanism of thegiven cylinder during a subsequent transition into a VDE mode (e.g.,when valve deactivation is subsequently commanded for the givencylinder) based on inferred latch pin movement parameters. As anexample, the engine controller may adjust a magnitude of the currentapplied to energize the solenoid during a subsequent valve deactivationoperation based on the inferred time taken for the latch pin to move tothe disengaged position, as well as based on how hard it hit. Forexample, the controller may reduce the current applied to energize thesolenoid so as to reduce the force with which the latch pin hits the endstop when entering the disengaged or engaged position, thereby reducingpin wear and extending component life. Following 734, method 700 ends.

In this way, the controller may disable and then re-enable the rockerarm mechanism all while the cam is on the base circle, causing no changein the valve lift. In doing so, the controller can measure theactivation time, and from that learn the solenoid response time, as wellas confirm that the e-latch rocker arm mechanism is functional withoutdisrupting engine operation.

Returning to 736, if the cam is at the beginning of the lift profile at738, the method includes monitoring for latch pin movement based on aninductive signature generated while energizing the e-latch solenoid. At740, based on the inductive signature generated during the solenoidenergization, it may be determined if latch pin movement was detected.As elaborated with reference to the table of FIG. 3, when the cam is onthe lift profile, the latch pin is not movable for transitioning from anengaged position to a disengaged position to deactivate a cylindervalve. That is, in response to solenoid energization, latch pin movementis not expected. If the inductive signature indicates that latch pinmovement was not detected (e.g., no decrease occurs during the currentrise during solenoid energization), then at 742, it may be inferred thatthe e-latch rocker arm mechanism is functional. Herein, the controllermay confirm that the latch pin is holding while the cam is at themaximum lift position. The method then ends.

If the inductive signature indicates that latch pin movement wasdetected, then at 744, it may be indicated that the e-latch rocker armmechanism is degraded. In particular, it may be inferred that the camlobe is worn or that there is a collapsed lifter. Indicating degradationmay include setting a diagnostic code, illuminating a light, and/or ornotifying a vehicle occupant via an information center. Also at 744, themethod includes, responsive to the indication of degradation, energizingthe e-latch solenoid to move the latch pin back to the engaged position.At 746, also responsive to the indication of degradation, the methodincludes preferentially deactivating the corresponding cylinder duringsubsequent VDE operation. For example, the corresponding cylinder mayexhibit a higher than average incidence of misfire due to the collapselifter or worn cam lobe. By preferentially deactivating thecorresponding cylinder, an overall occurrence of misfire during thesubsequent VDE operation may be reduced. As another example, thecontroller may choose to operate the engine smoothly but with the givencylinder deactivated over operating the engine roughly (e.g., with moreNVH) with all of the cylinders active. In still further examples, thecontroller may compare a fuel economy and/or NVH of operating the enginewith all cylinders active to operating the engine with the givencylinder deactivated and select the state that provides the highest fueleconomy and/or lowest NVH. The method then ends.

In this way, the controller may actively and opportunistically inducelatch pin movement when transition to and from a VDE state is notcommanded and then correlate VDE mechanism functionality with latch pinmovement. In particular, the controller can detect latch pin movementwhile the cam is on the base circle and when the state of the rocker armdoes not matter. The controller may energize the solenoid to move thelatch pin to the disengaged position (to move the valve to a deactivatedstate) and then again energize the solenoid to move the latch pin backto the engaged position (to move the valve to an active state), and usethe detected opening and closing times for diagnosing the e-latchmechanism and learning solenoid response times. Likewise, the controllercan detect latch pin movement (or a lack thereof) while the cam is onlift, wherein the solenoid is energized to attempt to move the latch pinto the disengaged position. The controller may correlate the detectionof no movement to confirm that the latch pin stays latched due to thee-latch mechanism being functional. Should latch pin movement occur,indicating degradation of the e-latch rocker arm mechanism, the solenoidmay then again be energized to move the latch pin back to the engagedposition (to move the valve to an active state).

Next, FIG. 8 shows an example graph 800 of crankshaft position sensoroutput and camshaft position sensor output relative to a piston positionand stroke of each cylinder of a four-cylinder engine. A piston positionof cylinder 1 is shown in plot 802, a piston position of cylinder 2 isshown in plot 808, a piston position of cylinder 3 is shown in plot 814,a piston position of cylinder 4 is shown in plot 820, crankshaftposition sensor output is shown in plot 826, and camshaft positionsensor output is shown in plot 828. For all of the above plots, thehorizontal axis represents crank angle (e.g., in degrees of thecrankshaft), with crank angle increasing along the horizontal axis fromleft to right. In the example of graph 800, 0 crank angle degrees isdefined as TDC of the intake stroke of cylinder 1, and the engine has afiring order of 1-3-4-2. The vertical axis represents each labeledparameter, with a value of the labeled parameter increasing along thevertical axis from bottom to top. Furthermore, a timing region whereinan intake valve e-latch rocker arm mechanism latch pin of cylinder 1 isimmovable is shown by shaded region 804, a timing region wherein anexhaust valve e-latch rocker arm mechanism latch pin of cylinder 1 isimmovable is shown by shaded region 806, a timing region wherein anintake valve e-latch rocker arm mechanism latch pin of cylinder 2 isimmovable is shown by shaded region 810, a timing region wherein anexhaust valve e-latch rocker arm mechanism latch pin of cylinder 2 isimmovable is shown by shaded region 812, a timing region wherein anintake valve e-latch rocker arm mechanism latch pin of cylinder 3 isimmovable is shown by shaded region 816, a timing region wherein anexhaust valve e-latch rocker arm mechanism latch pin of cylinder 3 isimmovable is shown by shaded region 818, a timing region wherein anintake valve e-latch rocker arm mechanism latch pin of cylinder 4 isimmovable is shown by shaded region 822, and a timing region wherein anexhaust valve e-latch rocker arm mechanism latch pin of cylinder 4 isimmovable is shown by shaded region 824. A crankshaft reference edge isindicated by a long-dashed line 830, and a camshaft reference edge isindicated by a short-dashed line 832.

Each of the four cylinders completes all four strokes (e.g., intake,compression, power, and exhaust) once every 720 crank angle degrees, oronce every two full rotations of the crankshaft. A crankshaft positionsensor (e.g., Hall effect sensor 120 of FIG. 1) is configured to sensethe presence or absence of equally spaced teeth on a toothed disc orwheel coupled to the crankshaft (e.g., a pulse-wheel). As the crankshaftrotates, each time a tooth passes the crankshaft position sensor, thevoltage output of the sensor switches from near zero voltage (off) tomaximum voltage (on) in a square wave, as shown in plot 826. A gap inthe teeth placed at a known crankshaft position, resulting in a gap inthe square wave, serves as a position reference for the crankshaftposition sensor. For example, between 0 and 180 crank angle degrees, thecrankshaft position sensor output (plot 826) shows the square wave.Between 180 and 270 crank angle degrees (e.g., at around 230 crank angledegrees), the gap in the square wave occurs due to the missing teeth ofthe crankshaft pulse-wheel. The return of the square wave after the gap(e.g., at around 250 crank angle degrees) creates the crankshaftreference edge 830. As an example, such as illustrated in FIG. 8, thegap may have a window of 20 crank angle degrees. As another example, thegap may have a window of 12 crank angle degrees. The controller may usea combination of the presence, absence, and return of the square wave toidentify the crankshaft reference edge 830. For example, the absence ofthe square wave alone or the absence and then presence of the squarewave may not reliably denote the crankshaft reference edge 830.Therefore, depending on a starting position of the crankshaft, it maytake a variable duration (or crankshaft rotation) for the controller todetect the presence, absence, and return of the crankshaft positionsensor square wave.

The crankshaft reference edge occurs once every 360 crank angle degrees.For example, as shown in FIG. 8, a second crankshaft reference edge 830occurs at around 610 crank angle degrees. Therefore, the crankshaftreference edge 830 alone does not reveal the stroke of each cylinder.For example, cylinder 1 may be in a compression stroke or an exhauststroke when the crankshaft reference edge 830 is identified.

An intake camshaft and an exhaust camshaft each rotate once per 720crank angle degrees (e.g., once per four-stroke engine cycle). Each ofthe intake camshaft and the exhaust camshaft may have a toothed disc orwheel (e.g., a pulse-wheel) coupled thereto, the rotation of which maybe sensed by a corresponding camshaft position sensor (e.g., camshaftposition sensors 155 and 157 shown in FIG. 1). Particularly, thecamshaft pulse-wheel may include variably sized teeth that are unequallyspaced such that some teeth are positioned closer to one another whileother teeth are positioned farther away from one another. Unequal pulsedurations and spacing among the pulses in a resulting pulsetrain, shownin plot 828, creates the camshaft reference edge 832, which occurs onceper 720 crank angle degrees. The camshaft reference edge 832 maycorrespond to a particular orientation the crankshaft and piston stroke,such as near TDC of the compression stroke of cylinder 1. Similar todetermining the crankshaft position, the controller may use signal datafrom before and after the camshaft reference edge in order toconclusively identify the camshaft reference edge and determine thecamshaft position therefrom. Furthermore, a falling edge of each campulse-wheel tooth may be equally spaced throughout 720 crank angledegrees while the rising edges may be spaced in a defined pattern thatthe controller may identify and synchronize with crank position signals.In an alternative example, the rising edges may be equally spaced whilethe falling edges are spaced in the defined pattern.

The output of only one camshaft position sensor (which could be eitherthe exhaust camshaft position sensor or the intake camshaft positionsensor) is shown in FIG. 8 (plot 828), as the pulsetrain output by theexhaust camshaft position sensor has the same timing as the pulsetrainoutput by the intake camshaft position sensor in this example. However,in other examples, such as when variable cam timing is used, the outputof the exhaust camshaft position sensor may be shifted relative to theoutput of the intake camshaft position sensor.

Unlike the crankshaft reference edge 830, which occurs at a definedposition once per 360 crank angle degrees, and the camshaft referenceedge 832, which occurs at a defined position once per 720 crank angledegrees, an inductive signature of an e-latch solenoid of each intakevalve and an inductive signature of an e-latch solenoid of each exhaustvalve provide piston stroke information throughout the 360 degreecrankshaft rotation and the 720 camshaft rotation. For example, at anygiven crankshaft position and camshaft position, one cylinder is in anintake stroke, during which the intake valve latch pin is immovable, andone cylinder is in an exhaust stroke, during which the exhaust valvelatch pin is immovable. As summarized with respect to table 300 of FIG.3, when a corresponding cam is positioned on its lobe, the latch pin isnot movable regardless of an activation state of the valve. Therefore,if an intake valve e-latch solenoid is energized and the correspondinglatch pin does not move, as determined from an inductive signature ofthe solenoid, it may be inferred that the corresponding cylinder is inits intake stroke. Similarly, if an exhaust valve e-latch solenoid isenergized and the corresponding latch pin does not move, it may beinferred that the corresponding cylinder is in is exhaust stroke. Forexample, if the intake valve e-latch solenoid of each cylinder isenergized at 90 crank angle degrees, the latch pin of the intake valveof cylinder 1 will not move (shaded region 804) while the latch pins ofthe intake valves of cylinders 2, 3, and 4 will move. As anotherexample, if the exhaust valve e-latch solenoid of each cylinder isenergized at 400 crank angle degrees, the latch pin corresponding to theexhaust valve of cylinder 2 will not move (shaded region 812) while thelatch pins of the exhaust valves of cylinders 1, 3, and 4 will move.Note that the shaded timing regions shown in FIG. 8 are exemplary innature and in other examples, the timing and duration may vary.

Turning now to FIG. 9, an example method 900 is shown for using ane-latch rocker arm mechanism (e.g., e-latch rocker arm mechanism 202 ofFIGS. 2A-2D) for camshaft position detection in a fixed cam engine.Camshaft position detection via the e-latch mechanism may be used todiagnose an existing camshaft position sensor, replace a camshaftposition sensor, or to estimate camshaft timing during conditions whenthe output of the camshaft position sensor is not available or notreliable. By knowing the camshaft timing, fuel delivery precision can beincreased. The method of FIG. 9 enables camshaft position determinationwhen crankshaft position data is available, such as from a crankshaftposition sensor. In comparison, the method of FIG. 10 enables camshaftposition determination when crankshaft position data is not yetavailable.

At 902, the method includes estimating and/or measuring engine operatingconditions. These may include, for example, engine speed, engine load,torque demand, engine temperature, exhaust temperature, air-fuel ratio,MAP, MAF, ambient conditions such as ambient temperature, pressure, andhumidity, etc. At 904, it may be determined if a crankshaft position isknown. In one example, a crankshaft position is learned based on anoutput of a functional crankshaft position sensor (e.g., Hall effectsensor 120 of FIG. 1). During an engine start, it may take a variableamount of time for a controller to determine the crankshaft positionfrom the output of the crankshaft position sensor, with the amount oftime varying based on engine speed, ambient temperature, and a startingposition of the crankshaft, for example. As one example, if thecrankshaft position sensor is receiving pulses that indicate thecrankshaft is rotating, but has not yet encountered the gap or referenceedge, the controller will not know the position of the crankshaft. Asanother example, the crankshaft position sensor may not provide areliable signal due to sensor degradation, such as due to a looseelectrical connection to the sensor. If the crankshaft position is notyet known, or if the crankshaft position sensor is degraded, then at906, the method includes using the cylinder valve deactivation mechanismto determine the crankshaft position. As elaborated at FIG. 10, thisincludes inferring the crankshaft position based in part on an inductivesignature of each intake valve e-latch solenoid, the signature generatedupon energizing the solenoid of each engine cylinder's intake valve.

If the crankshaft position is known, at 908, the method includesenergizing an e-latch solenoid of an exhaust valve corresponding to acylinder with its piston near the beginning of its upstroke, just afterBDC. The BDC point may be inferred based on the sensed crankshaftposition. In a fixed cam engine, the camshaft spins at one-half of theengine speed (e.g., the camshaft rotates once per 720 crankshaftdegrees). Using a four-cylinder engine as an example, a first set of twocylinders will have pistons starting an upstroke while a second set oftwo cylinders will have pistons starting a downstroke at a first engineposition (e.g., 180 crank angle degrees), as shown in FIG. 8. Similarly,the pistons of the first set of two cylinders will be starting adownstroke while the pistons of the second set of two cylinders will bestarting an upstroke at a second engine position that is 180 crank angledegrees later (e.g., at 360 crank angle degrees). Of the two cylindersin the upstroke at the given crankshaft position, one cylinder is in theexhaust stroke while the other is in the compression stroke, but thecrankshaft position alone does not distinguish between the two.

The e-latch solenoid corresponding to the exhaust valve of a cylinderhaving its piston in an upstroke may be energized with a voltage pulseto attempt to move a latch pin of the e-latch rocker arm mechanism. Asdescribed with respect to FIGS. 2A-2D and summarized in the table ofFIG. 3, the latch pin may move between an engaged and a disengagedposition when a corresponding cam is on a base circle but not when thecam is on a lobe. During the compression stroke, the exhaust valve camis on the base circle and is therefore movable, but during the exhauststroke, the exhaust valve cam is on the lobe and is therefore immovable.Therefore, assuming the current position of the latch pin is known, thecontroller may energize the exhaust valve e-latch solenoid with voltageof an appropriate polarity for eliciting movement. For example, if thelatch pin is in the engaged position, the e-latch solenoid may beenergized with voltage of a first polarity to attempt to move the latchpin to the disengaged position. In another example, if the latch pin isin the disengaged position, the e-latch solenoid may be energized withvoltage of a second polarity, opposite of the first polarity, to attemptto move the latch pin to the engaged position. If the current positionof the latch pin is unknown, then the latch pin position may be resetprior to performing method 900, such as according to the method of FIG.4.

At 910, the method includes monitoring for latch pin movement via aninductive signature of the e-latch solenoid during the energization. Theinductive signature refers to a measured current through the e-latchsolenoid during the energization. If the cam is on the base circle andthe associated latch pin moves, the movement causes the current tomomentarily decrease (e.g., a slope of the current changes), whichappears as a valley in the solenoid current during the energization, asillustrated with respect to FIG. 14. In contrast, when the cam is on thelobe and the associated latch pin does not move, the solenoid currentwill steadily increase without a valley until a maximum current isreached.

At 912, it may be determined whether latch pin movement was detectedbased on the generated inductive signature. In one example, latch pinmovement may be confirmed if the inductive signature includes a valleyin the measured solenoid current and/or a change in the slope of thesolenoid current, and a lack of latch pin movement may be confirmed ifthe inductive signature includes a steady increase (e.g., without adecrease) until the maximum current is reached.

If latch pin movement is confirmed, then at 914, the method includesindicating that the piston of the given cylinder is in a compressionstroke. At 916, upon indicating that the piston is in the compressionstroke, the method includes energizing the exhaust valve e-latchsolenoid to return the latch pin of the given cylinder to the previousposition. For example, if the exhaust valve latch pin started in theengaged position, then it may be returned to the engaged position viaenergizing the associated solenoid with a voltage pulse of the secondpolarity. In another example, if the exhaust valve latch pin started inthe disengaged position, then it may be returned to the disengagedposition via energizing the associated solenoid with a voltage pulse ofthe first polarity. In this way, an inadvertent valve change of state(e.g., from active to deactivated or from deactivated to active) may beavoided.

Returning to 912, if latch pin movement is not confirmed, then at 918,the method includes indicating that the piston of the given cylinder isin an exhaust stroke. From each of 916 and 918, the method moves to 920and includes inferring the camshaft position based on the crankshaftposition (sensed from the crankshaft position sensor) and the indicatedpiston stroke. As one example, referencing FIG. 8, if the crankshaft issensed to be at the reference edge 830, then it could be at either 250degrees or 610 degrees. If the solenoid for an exhaust valve on cylinder1 was energized and it was detected that the latch pin had moved, thenit may be determined that cylinder 1 was on the compression stroke andtherefore, the crankshaft is at angle 250 and not angle 610. As anotherexample, if the latch pin of the exhaust valve on cylinder 1 did notmove in response to the energization, it may be determined that cylinder1 was on the exhaust stroke and therefore, the crankshaft is at angle610 and not angle 250.

Although the controller may determine the piston stroke (and then thecamshaft position from the crankshaft position and the piston stroke)from energizing the exhaust valve e-latch solenoid corresponding to onecylinder, in other examples, the exhaust valve e-latch solenoids of morethan one cylinder may be energized, such as two cylinders with pistonsin their upstrokes, or every cylinder. In such an example, the lack ofmovement of the exhaust valve latch pin determines the piston stroke(e.g., the exhaust stroke).

In an alternative example, an intake valve e-latch solenoid may beenergized in an analogous fashion while the piston is in a downstroke.For example, with the piston starting a downstroke, the given cylinderis either in an intake stroke, during which a corresponding intake camis on the lobe and the latch pin is immovable, or a power stroke, duringwhich the corresponding intake cam is on the base circle or the latchpin is movable. Based on whether or not the inductive signature of theintake valve e-latch solenoid indicates latch pin movement, thecontroller may distinguish between the power stroke (e.g., latch pinmovement is confirmed) and the intake stroke (e.g., a lack of latch pinmovement is confirmed). In some examples, the controller maypreferentially determine the camshaft timing using the exhaust valvedeactivation mechanism over the intake valve deactivation mechanism (andvice versa) based on desired valve states during start up, operatingconditions, etc.

In this way, camshaft timing may be accurately detected without needingto rely on a camshaft sensor, although such a sensor may be used inaddition. Further, by not relying on misfire detection or crankshaftacceleration data for determining a camshaft timing, exhaust emissionscan be improved.

Turning now to FIG. 10, an example method 1000 is shown for using thee-latch mechanism for camshaft and crankshaft position detection. Byknowing the camshaft timing, fuel delivery precision can be improved.The method of FIG. 10 enables camshaft position determination whencrankshaft position data is not available, such as when an engine hasbeen restarted from rest. Method 1000 may be performed as a part ofmethod 900 of FIG. 9 (e.g., at 906).

At 1002, the method includes estimating and/or measuring engineoperating conditions. These may include, for example, engine speed,engine load, torque demand, engine temperature, exhaust temperature,air-fuel ratio, ambient conditions such as ambient temperature,pressure, and humidity, etc. Engine operating conditions may furtherinclude intake and exhaust valve operational states. A latch pinposition (e.g., engaged or disengaged, when the valve is active ordeactivated, respectively) of each valve e-latch rocker arm mechanismmay be inferred from the intake and exhaust valve operational states. Ifthe current intake valve and exhaust valve operational states areunknown, the controller may reset the corresponding latch pins accordingto the method of FIG. 4, for example.

At 1004, it may be determined if an engine start condition is present.For example, it may be determined if a key-on event has occurred, if astarter motor has been engaged to crank the engine unfueled, and/or ifthe engine speed is at or below an engine cranking speed. If an enginestart is not confirmed, the method moves to 1006 to maintain operatingparameters. At this time, crankshaft position is unavailable andundeterminable, and therefore camshaft position determination is alsonot possible.

If an engine start is confirmed, then at 1008, the method includesenergizing an intake valve e-latch solenoid of each engine cylinder andmonitoring the corresponding inductive signature generated upon theenergization for latch pin movement. For example, if the intake valvelatch pin is in the engaged position, the corresponding solenoid may beenergized with a voltage pulse of a first polarity to attempt to movethe latch pin to the disengaged position. In another example, if theintake valve latch pin is in the disengaged position, the correspondingsolenoid may be energized with a voltage pulse of a second polarity,which is opposite of the first polarity, to attempt to move the latchpin to the engaged position. As described above at 910 of FIG. 9, adecrease in the inductive signature is indicative of latch pin movement.If the intake valve latch pin moves, the corresponding cylinder may bein its exhaust, compression, or power stroke, during which acorresponding intake cam is on base circle and latch pin movement ispossible. If the intake valve latch pin does not move, the correspondingcylinder is inferred to be in its intake stroke, during which thecorresponding intake cam is on the lobe and latch pin movement does notoccur. Using a four-cylinder engine as an example, at any (unknown)crankshaft position, one cylinder is in an intake stroke. Once theintake stroke cylinder is identified, strokes of the remaining cylindersmay be inferred based on a known firing order of the engine. At 1009,method 1000 optionally includes re-energizing the intake valve e-latchsolenoid corresponding to the latch pins that moved in order to actuatethe corresponding latch pins to the previous position. If a change inintake valve state is not desired, returning the latch pins to theprevious (e.g., starting) position prevents inadvertently deactivating(when the starting position is the engaged position) or activating (whenthe starting position is the disengaged position) the correspondingintake valves, for example. If the latch pins started in the engagedposition, then the corresponding solenoids may be energized with avoltage pulse of the second polarity to move the latch pin from thedisengaged position back to the engaged position. If the latch pinsstarted in the disengaged position, then the corresponding solenoids maybe energized with a voltage pulse of the first polarity to move thelatch pin from the engaged position back to the disengaged position. Inanother example, when a change in the intake valve state is desired,1009 may be omitted.

At 1010, the method includes determining the crankshaft position basedon at least two of a crankshaft position sensor output, an intakecamshaft position sensor output, and the inductive signature of eachintake valve e-latch solenoid. The controller may select the first twosignals of the crankshaft position sensor output, the intake camshaftposition sensor output, and the inductive signature of each intake valvee-latch solenoid that give usable information for determining thecrankshaft position. For example, it may take a variable duration forthe controller to identify a characteristic crankshaft reference edgesignal (e.g., a “sync-pulse”) from the crankshaft position sensor outputand a characteristic camshaft reference edge signal from the camshaftposition sensor output based on a starting position of the engine,engine speed, and ambient temperature. In contrast, the inductivesignature of each e-latch solenoid reveals which cylinder is in theintake stroke at any (unknown) engine position.

Returning briefly to FIG. 8, as an example, if the engine startingposition is 450 degrees, the inductive signature of each intake valvee-latch solenoid would identify cylinder 4 as in the intake stroke(shaded region 822). This piston stroke identification may be combinedwith the next change in signal from the camshaft position sensor todetermine the crank angle. For example, moving forward from (unknown)crankshaft angle 450, the next change in camshaft signal occurs at angle530 where the signal changes from high to low. Combining the informationthat cylinder 4 was on the intake stroke with the detection of atransition from high to low of the camshaft signal results in thedetermination that the engine is at angle 530 at that moment.Determining the crankshaft signal to this level of accuracy requiresthat either the intake camshaft be a fixed camshaft (e.g., not able tobe varied or phased relative to the crankshaft), or that the camshaft isknown to be in a particular phased position, such as a default lockedposition, when method 1000 is executed. The pulses from the crankshaftsignal can be used to update the angle of the crankshaft and thecamshaft from that point forward. As another example, if the enginestarting position is 200 degrees, the inductive signature of each intakevalve e-latch solenoid would identify cylinder 3 as in the intake stroke(shaded region 816). This piston stroke identification may be combinedwith the signals from the crankshaft as it turns to identify the nextcrankshaft reference edge as being angle 250. As still another example,the crankshaft position sensor output may be combined with the camshaftposition sensor output when a crankshaft reference edge and camshaftsignal state are available prior to the interpretation of an inductivesignature from the energization of latch pin solenoids.

Returning to FIG. 10, at 1012, the method includes determining theintake camshaft position for each cylinder based on the inductivesignature of each intake valve e-latch solenoid and further based on oneof the inferred crankshaft position and the intake camshaft positionsensor output. For example, the inferred crankshaft position and theinferred cylinder stroke (e.g., as determined from the inductivesignature of each intake valve e-latch solenoid) may be used todetermine the rotational orientation of the intake camshaft relative tothe crankshaft, particularly when the camshaft position sensor is notincluded or when the camshaft position sensor output has not yetidentified the camshaft position. If the intake camshaft is a fixedcamshaft that cannot vary its angular position relative to thecrankshaft, then its position can be directly calculated once thecrankshaft position is known. In an alternative example, if the intakecamshaft is able to be varied using a camshaft phasing mechanism and thecamshaft position sensor is included, then the known crankshaft positioninformation can be combined with the signal from the camshaft positionsensor to determine the camshaft position, and the inductive signaturemay not be used to determine the intake camshaft position.

At 1014, the method includes determining the exhaust camshaft positionfor each cylinder based on the inferred intake camshaft position. Forexample, the exhaust camshaft position may be at a known offset (e.g.,rotated a number of degrees) from the intake camshaft position. Theexhaust camshaft position may then be determined from the inferredintake camshaft position and the known offset. In another example, theintake cam and the exhaust cam may be included on a single camshaft. Themethod then ends.

In an alternative example, the exhaust valve e-latch solenoid of eachcylinder may be energized in an analogous fashion during the crankshaftposition learning. If the exhaust valve latch pin moves, thecorresponding cylinder may be in its intake, compression, or powerstroke, during which a corresponding exhaust cam is on base circle andlatch pin movement is possible. If the exhaust valve latch pin does notmove, the corresponding cylinder is inferred to be in its exhauststroke, during which the corresponding exhaust cam is on the lobe andlatch pin movement does not occur. Using a four-cylinder engine as anexample, at any (unknown) crankshaft position, one cylinder is in anexhaust stroke. Once the exhaust stroke cylinder is identified, strokesof the remaining cylinders may be inferred based on a known firing orderof the engine. In some examples, the controller may preferentiallydetermine the crankshaft position using the exhaust valve deactivationmechanism over the intake valve deactivation mechanism (and vice versa)based on desired valve states during start up, operating conditions,etc.

In this way, crankshaft and camshaft timing may be accurately detectedwith or without a camshaft sensor. The e-latch rocker arm mechanismprovides an additional signal from which the crankshaft position and/orthe camshaft position can be determined, which may enable the crankshaftposition and/or the camshaft position to be determined quickly andreliably. Thereby, fuel injection timing and ignition timing may beaccurately controlled, and engine start times may be decreased. Further,by not relying on misfire detection or crankshaft acceleration data fordetermining the camshaft position, exhaust emissions can be improved.

Next, FIG. 11 shows an example graph 1100 of setting intake valves of afour-cylinder engine to a desired operational state during an enginestart. For example, the intake valves may be set to the desiredoperational state in response to an engine start request and beforeintake valve camshaft timing is known, such as according to the examplemethod of FIG. 4. Although the example of graph 1100 shows setting theintake valves to the desired operational state, it should be understoodthat exhaust valves may also be set to a desired operational stateduring the engine start, which may be different than the desired intakevalve operational state in some examples. Furthermore, in some examples,the desired intake valve and/or exhaust valve operational state may notbe the same for every cylinder. Intake cam lift of cylinder 1 is shownin plot 1102, intake valve solenoid voltage of cylinder 1 is shown inplot 1104, intake cam lift of cylinder 2 is shown in plot 1106, intakevalve solenoid voltage of cylinder 2 is shown in plot 1108, intake camlift of cylinder 3 is shown in plot 1110, intake valve solenoid voltageof cylinder 3 is shown in plot 1112, intake cam lift of cylinder 4 isshown in plot 1114, intake valve solenoid voltage of cylinder 4 is shownin plot 1116, a desired intake valve state (e.g., for the intake valvesof all four cylinders) is shown in plot 1118, and engine status is shownin plot 1120. For all of the above, the horizontal axis represents time,with time increasing along the horizontal axis from left to right. Thevertical axis represents each labeled parameter, with the value of thelabeled parameter increasing along the vertical axis from bottom to top,with the exceptions of plot 1118, in which the vertical axis representswhether the desired valve state is active or deactivated, as labeled,and plot 1120, in which the vertical axis represents whether the engineis on (e.g., operating at a non-zero speed, with combustion occurring inthe engine cylinders) or off (e.g., at rest, without combustionoccurring in the cylinders). In plots 1102, 1106, 1110, and 1114, intakecam lift refers to a radius from a base circle of the cam (e.g., on alobe of the cam, such as lobe 151 b of FIGS. 2A-2D), which varies as thecam is rotated against a cam follower during engine operation.

Prior to time t1, the engine is off, as shown in plot 1120. During theprior engine shutdown, the intake valves were kept in the active state(plot 1118), enabling each intake valve to open in response to intakecam lift. For example, a latch pin of each intake valve e-latch rockerarm mechanism is in an engaged position, as illustrated with respect toFIGS. 2A-2D and summarized in the table of FIG. 3. While the engine isoff, the intake cam of each cylinder does not rotate. The intake cams ofcylinder 1 (plot 1102), cylinder 3 (plot 1110), and cylinder 4 (plot1114) are on their base circles, as illustrated by zero intake cam lift.Therefore, a corresponding intake valve e-latch rocker arm mechanism isunloaded for each of cylinders 1, 3, and 4, and latch pins of each ofthe e-latch rocker arm mechanisms are moveable. The intake cam ofcylinder 2 (plot 1106) is on its lobe, as illustrated by the non-zerointake cam lift. Therefore, a corresponding intake valve e-latch rockerarm mechanism is loaded, and the latch pin of the intake valve e-latchrocker arm mechanism of cylinder 2 is immovable.

At time t1, an engine start is requested, and the engine status changesto on (plot 1120). In response to the engine start request, intake valvedeactivation is desired (plot 1118) in order to reduce an air springwithin each cylinder during the engine start. However, an enginecontroller (e.g., controller 12 of FIG. 1) may no longer know the camposition of each intake valve, such as the lifted position of the intakecam of cylinder 2 (plot 1106), and may no longer know the latch pinposition of each intake valve e-latch rocker arm mechanism. Between timet1 and time t2, a solenoid of each intake valve e-latch rocker armmechanism is energized with a voltage pulse having a first polarity(e.g., positive voltage) in order to attempt to move any latched latchpins into a disengaged position (plots 1104, 1108, 1112, and 1116). Dueto the intake cams of cylinders 1, cylinder 3, and cylinder 4 being onthe base circle (plots 1102, 1110, and 1114, respectively), the latchpins of the corresponding intake valve e-latch rocker arm mechanismsmove from the engaged to the disengaged position that deactivates thevalves. If the inductive signature of each solenoid is monitored, thelatch pin movement appears as a momentary decrease in the solenoidcurrent, as will be shown in FIG. 12. Due to the intake cam of cylinder2 being lifted during the energization (e.g., between time t1 and timet2), the intake valve latch pin of cylinder 2 does not move. Therefore,by time t2, the intake valves of cylinders 1, 3, and 4 are deactivatedwhile the intake valve of cylinder 2 remains active, with its latch pinin the engaged position.

At time t3, a threshold rotation indicated by line 1122 is reached. Asdescribed with respect to FIG. 4, the threshold rotation corresponds toa maximum valve duration after which any lifted cam will be returned tothe base circle. Therefore, the intake valve e-latch solenoid of eachcylinder is re-energized with a voltage pulse of the first polaritybetween time t3 and time 4 (plots 1104, 1108, 1112, and 1116). At timet3, the intake cam of cylinder 2 is no longer lifted (plot 1106), and sothe intake valve latch pin of cylinder 2 moves from the engaged to thedisengaged position. Because the intake valves of cylinders 1, 3, and 4are already deactivated, with their corresponding intake valve latchpins in the disengaged position, re-energizing their intake valvee-latch solenoids with the voltage pulse of the first polarity does notfurther move the corresponding latch pins or alter the valve operationalstate. Thus, by time t4, all of the intake valves are deactivated. Inthis way, the engine start is facilitated by deactivating the cylinderintake valves even without knowledge of the cam position of eachcylinder or the starting valve state.

FIG. 12 shows an example graph 1200 of diagnosing a cylinder valvedeactivation mechanism during an engine transition to and from a VDEmode of operation. For example, the engine may be transitioned betweenthe VDE mode of operation and a non-VDE mode of operation according tothe method of FIG. 5, and the cylinder valve deactivation mechanism maybe diagnosed according to the method of FIGS. 6A-6B. Engine speed isshown in plot 1202, a commanded valve state is shown in plot 1204, camlobe lift is shown in plot 1206, solenoid voltage is shown in plot 1208,solenoid current is shown in plot 1210, a position of a latch pin isshown in plot 1212, and an indication of valve deactivation mechanismdegradation is shown in plot 1214. For all of the above, the horizontalaxis represents time, with time increasing along the horizontal axisfrom left to right. The vertical axis represents each labeled parameter,with a value of each labeled parameter increasing along the verticalaxis from bottom to top, with the exceptions of plot 1204, in which thevertical axis shows the commanded valve state (e.g., “active” or“deactivated,” as labeled), and plot 1212, in which the vertical axisshows the latch pin position (e.g., “engaged” or “disengaged,” aslabeled).), and plot 1214, in which the vertical axis shows whetherdegradation is indicated (e.g., “yes” or “no”). In the example of graph1200, the commanded valve state (plot 1204), cam lobe lift (plot 1206),solenoid voltage (plot 1208), solenoid current (plot 1210), and latchpin position (plot 1212), and indication of valve deactivation mechanismdegradation (plot 1214) are shown for a single valve, which may be acylinder exhaust valve or a cylinder intake valve. It should beunderstood that a plurality of valves may be controlled simultaneouslyand operated similarly.

Prior to time t1, the engine is on and operating at a non-zero speed(plot 1202) that is greater than a threshold speed for performing a lowspeed VDE mechanism diagnostic, indicated by a dashed line 1216.Therefore, valve deactivation mechanisms (such as valve deactivationmechanism 252 of FIGS. 2A-2D) may be diagnosed when a valve change ofstate is commanded and not when a valve change of state is notcommanded. Also prior to time t1, the valve is in an active commandedvalve state (plot 1204). A latch pin of the valve deactivation mechanism(e.g., latch pin 214 of FIGS. 2A-2D) is in an engaged position (plot1212), enabling the valve to open as a result of cam lobe lift (plot1206), as described with respect to FIG. 2C.

At time t1, valve deactivation is commanded (plot 1204), such as tooperate the engine in the VDE mode. In response to the change in thecommanded valve state, a solenoid of the valve deactivation mechanism(e.g., solenoid 216 of FIGS. 2A-2D) is energized with a voltage pulsehaving a first (e.g., positive) polarity (plot 1208). As the solenoid isenergized, the solenoid current increases (plot 1210), generating aninductive signature. As the solenoid current increases, a magnetic fieldof the solenoid expands and acts on the latch pin. Because the cam lobelift is zero, indicating that the cam is on its base circle (e.g., basecircle 151 a shown in FIGS. 2A-2D), the corresponding latch pin isexpected to move due to a force of the magnetic field.

During the energization, at time t2, the solenoid current (plot 1210)begins to decrease (e.g., a slope of the current changes), signifyingmovement of the latch pin. At time t3, the solenoid current (plot 1210)reaches a local minimum, indicating that the latch pin has completed itsmovement from the engaged to a disengaged position (plot 1212). Thus,characteristics of the solenoid current (plot 1210) show an inductivesignature indicative of latch pin movement, as expected, and valvedeactivation mechanism degradation is not indicated (plot 1214).

After time t3, the solenoid current (plot 1210) increases until amaximum current is reached and then decays following completion of thevoltage pulse (plot 1208). With the latch pin in the disengagedposition, the corresponding valve is deactivated and will not open inresponse to cam lobe lift, as described with respect to FIG. 2D. Aduration between time t1 and time t3 corresponds to a solenoid responsetime (e.g., an amount of time it takes from energizing the solenoid tothe latch pin completing its movement.). A controller may learn thesolenoid response time for part-to-part adaptation and operating in anincreased RPM range, as described with respect to FIG. 6A.

However, if the valve deactivation mechanism is degraded, the inductivesignature of the solenoid current may indicate that the latch pin hasnot moved in response to the solenoid energization, such as shown inshort-dashed segment 1210 a. In short-dashed segment 1210 a, thesolenoid current increases until the maximum is reached, withoutdecreasing at time t2 and without reaching the local minimum at time t3.As such, the inductive signature of the solenoid indicates no latch pinmovement despite the latch pin being moveable (e.g., the cam lobe liftis zero). The latch pin is stuck in the engaged position (short-dashedsegment 1212 a), and degradation of the valve deactivation mechanism isindicated (short-dashed segment 1214 a).

At time t4, valve activation is commanded (plot 1204). For example, theengine may be transitioning to a non-VDE mode of operation. While thevalve activation is commanded, the cam lobe lift (plot 1206) is near amaximum lift. With the cam lobe lift near the maximum lift, acorresponding rocker arm is loaded, and latch pin movement is notexpected in response to solenoid energization. Therefore, the controllermay wait until the cam is near the base circle to begin theenergization.

At time t5, as the cam lobe lift decreases (plot 1206) and approaches areturn to its base circle, the solenoid is energized with a voltagepulse having a second (e.g., negative) polarity (plot 1208) such thatthe latch pin may be pulled to the engaged position as soon as the camreturns to the base circle and the associated rocker arm becomesunloaded. At time t7, the solenoid current begins to decrease (plot1210) as the cam lobe reaches base circle and the latch pin begins tomove. The controller may log a cam angle at time t7 to confirm the camposition. At time t8, the local minimum in the solenoid current (plot1210) shows that the latch pin has completed its movement back to theengaged position (plot 1212). Because the latch pin moved when the camreturned to base circle (e.g., a cam lobe lift of zero), as expected,valve deactivation mechanism degradation is not indicated (plot 1214).

If the solenoid current decreases sooner than expected at time t6, asshown in dashed segment 1210 c, a worn cam lobe may be detected. Theworn cam lobe results in a smaller cam lobe lift and a quicker return tobase circle, as shown by dashed segment 1206 c, and an earliertransition of the latch pin from the disengaged to the engaged position(dashed segment 1212 c). In response to the detection of the worn camlobe, the controller may preferentially deactivate the correspondingcylinder, as described with respect to FIG. 6A. In this way, degradationof the valve deactivation mechanism and the cam itself may beidentified.

Next, FIG. 13 shows an example graph 1300 of diagnosing a cylinder valvedeactivation mechanism during low speed engine operation and without acommanded change in valve operating state, such as according to themethod of FIG. 7. Engine speed is shown in plot 1302, a commanded valvestate is shown in plot 1304, cam lobe lift is shown in plot 1306,solenoid voltage is shown in plot 1308, solenoid current is shown inplot 1310, a position of a latch pin is shown in plot 1312, and anindication of valve deactivation mechanism degradation is shown in plot1314. For all of the above, the horizontal axis represents time, withtime increasing along the horizontal axis from left to right. Thevertical axis represents each labeled parameter, with a value of eachlabeled parameter increasing along the vertical axis from bottom to top,with the exceptions of plot 1304, in which the vertical axis shows thecommanded valve state (e.g., “active” or “deactivated,” as labeled),plot 1312, in which the vertical axis shows the latch pin position(e.g., “engaged” or “disengaged,” as labeled), and plot 1314, in whichthe vertical axis shows whether degradation is indicated (e.g., “yes” or“no”). In the example of graph 1300, the commanded valve state (plot1304), cam lobe lift (plot 1306), solenoid voltage (plot 1308), solenoidcurrent (plot 1310), latch pin position (plot 1312), and indication ofvalve deactivation mechanism degradation (plot 1314) are shown for asingle valve, which may be a cylinder exhaust valve or a cylinder intakevalve. It should be understood that a plurality of valves may besimultaneously operated similarly.

Prior to time t1, the engine is on and operating at a non-zero speed(plot 1302) that is less than a threshold speed for performing a lowspeed VDE mechanism diagnostic, indicated by a dashed line 1316.Therefore, valve deactivation mechanisms (such as valve deactivationmechanism 252 of FIGS. 2A-2D) may be diagnosed when a valve change ofstate is not commanded. Also prior to time t1, the valve is in an activecommanded valve state (plot 1304). A latch pin of the valve deactivationmechanism (e.g., latch pin 214 of FIGS. 2A-2D) is in an engaged position(plot 1312), enabling the valve to open as a result of cam lobe lift(plot 1306), as described with respect to FIG. 2C.

At time t1, the cam lobe lift is zero (plot 1306), indicating that thecam is on its base circle (e.g., base circle 151 a shown in FIGS.2A-2D). Due to the low engine speed, there is enough time to actuate thelatch pin from the engaged position, to a disengaged position, and backto the engaged position before the cam rotates off of the base circleand onto its lobe (e.g., lobe 151 b shown in FIGS. 2A-2D). In order tocheck the valve deactivation mechanism for degradation, a solenoid ofthe valve deactivation mechanism (e.g., solenoid 216 of FIGS. 2A-2D) isenergized with a voltage pulse of a first (e.g., positive) polarity(plot 1308). As the solenoid is energized, the solenoid currentincreases (plot 1310), generating an inductive signature. As thesolenoid current increases, a magnetic field of the solenoid expands andacts on the latch pin. Because the cam lobe lift is zero and acorresponding e-latch rocker arm mechanism is unloaded, the latch pin isexpected to move due to a force of the magnetic field.

During the energization, at time t2, the solenoid current (plot 1310)begins to decrease (e.g., a slope of the current changes), signifyingmovement of the latch pin. At time t3, the solenoid current (plot 1310)reaches a local minimum, indicating that the latch pin has completed itsmovement from the engaged to the disengaged position (plot 1312). Thus,characteristics of the solenoid current (plot 1310) show an inductivesignature indicative of latch pin movement, as expected, and valvedeactivation mechanism degradation is not indicated (plot 1314).

After time t3, the solenoid current (plot 1310) increases until amaximum current is reached and then decays following completion of thevoltage pulse (plot 1308). A duration between time t1 and time t3corresponds to a solenoid response time (e.g., an amount of time ittakes from energizing the solenoid to the latch pin completing itsmovement). A controller may learn the solenoid response time forpart-to-part adaptation and operating in an increased RPM range, asdescribed with respect to FIG. 6A. With the latch pin in the disengagedposition, the corresponding valve is deactivated and will not open inresponse to cam lobe lift, as described with respect to FIG. 2D.However, valve deactivation is not desired, as indicated by thecommanded valve state remaining active (plot 1304). Therefore, at timet4, the solenoid is re-energized with a voltage pulse of a second (e.g.,negative) polarity to move the latch pin back to the engaged position.Movement of the latch pin from the disengaged to the engaged position isconfirmed by the inductive signature of the solenoid current (plot 1310)showing the characteristic current decrease at time t5 and local minimumat time t6 as the latch pin completes its movement to the engagedposition (plot 1312). With the latch pin successfully returned to theengaged position, valve deactivation mechanism degradation is notindicated (plot 1314).

However, if the valve deactivation mechanism is degraded, the inductivesignature of the solenoid current may indicate that the latch pin hasnot moved in response to the solenoid energization, such as shown inshort-dashed segment 1310 a (e.g., during the voltage pulse of the firstpolarity) and dot-dashed segment 1310 b (e.g., during the voltage pulseof the second polarity). In short-dashed segment 1310 a, the solenoidcurrent increases until the maximum is reached, without decreasing attime t2 and without reaching the local minimum at time t3. As such, theinductive signature of the solenoid indicates no latch pin movementdespite the latch pin being moveable (e.g., the cam lobe lift is zero,as shown in plot 1306). The latch pin is stuck in the engaged position(short-dashed segment 1312 a), and degradation of the valve deactivationmechanism degradation is (short-dashed segment 1314 a). Similarly, indot-dashed segment 1310 b, the solenoid current increases until themaximum is reached, without decreasing at time t5 and without reachingthe local maximum at time t6. As such, the inductive signature of thesolenoid indicates no latch pin movement despite the latch pin beingmoveable. The latch pin is stuck or already in the engaged position. Ifthe trace 1310 had been followed between time t1 and time t4, indicatingthat the latch pin successfully disengaged, then it can be concludedthat trace 1310 b indicates that the latch pin is stuck in thedisengaged position, and degradation of the valve deactivation mechanismis indicated (dot-dashed segment 1314 b). If however, trace 1310 a hadbeen followed between time t1 and time t4, then the latch pin did notmove to the disengaged position during that time. Trace 1310 b wouldthen indicate that the latch pin is still stuck in the engaged position.

The cam lobe lift (plot 1306) is on lift at time t7. With the cam lobelifted, a corresponding rocker arm is loaded, and latch pin movement isnot expected in response to solenoid energization. At time t7, thesolenoid is energized with a voltage pulse of the first polarity tocheck the valve deactivation mechanism for degradation, such as to seeif the latch pin is held in the engaged position while the rocker arm isloaded. During the energization, the solenoid current (plot 1310)increases until the maximum current is reached and without decreasing.Thus, the inductive signature indicates that the latch pin has not movedand remains in the engaged position (plot 1312), as expected, anddegradation of the valve deactivation mechanism is not indicated (plot1314). However, if the inductive signature shows the characteristicdecrease and local minimum indicative of latch pin movement, as indashed segment 1310 c, it may be inferred that the latch pinunexpectedly moved to the disengaged position (dashed segment 1312 c).In response to the inductive signature indicating latch pin movementwhile the cam is lifted, valve deactivation mechanism degradation isindicated (dashed segment 1314 c).

Next, FIG. 14 shows an example graph 1400 of determining camshaftposition based on an inductive signature of an e-latch rocker armmechanism solenoid when a crankshaft position is known, such asaccording to the method of FIG. 9. Piston position is shown in plot1402, exhaust cam lobe lift for a first example is shown in plot 1404,exhaust valve solenoid voltage for the first example is shown in plot1406, exhaust valve solenoid current for the first example is shown inplot 1408, and a position of a latch pin for the first example is shownin plot 1410. For comparison, exhaust cam lobe lift for a second exampleis shown in dashed plot 1405, exhaust valve solenoid voltage for thesecond example is shown in dashed plot 1407, exhaust valve solenoidcurrent for the second example is shown in dashed plot 1409, and aposition of a latch pin for the second example is shown in plot 1411.For all of the above, the horizontal axis represents time, with timeincreasing along the horizontal axis from left to right. The verticalaxis represents each labeled parameter, with a value of each labeledparameter increasing along the vertical axis from bottom to top, withthe exception of plots 1410 and 1411, in which the vertical axis showsthe latch pin position (e.g., “engaged” or “disengaged,” as labeled).Piston position (plot 1402) is shown with respect to bottom dead center(BDC) and top dead center (TDC).

At time t1, a controller (e.g., controller 12 of FIG. 1) determines aBDC position of a cylinder based on an output of a crankshaft positionsensor (not shown). However, the camshaft position is unknown, and sothe controller does not know if the piston is at BDC of an intake strokeor a power stroke. That is, the controller does not know if the exhaustcam of the cylinder has a lift profile shown in plot 1404 or dashed plot1405.

A latch pin of the exhaust valve e-latch rocker arm mechanism (e.g.,latch pin 214 of FIGS. 2A-2D) is known to be in the engaged position(plot 1410). As the piston rises in an upstroke, at time t2, the exhaustvalve e-latch solenoid is energized with a voltage pulse having a first(e.g., positive) polarity (plot 1406) to attempt to move the latch pinfrom the engaged to the disengaged position. The resulting solenoidcurrent is monitored for moment of the associated latch pin. In thefirst example, the cylinder is in an exhaust stroke, and the exhaust camlobe is lifted (plot 1404). With the exhaust cam lobe lifted, thecorresponding exhaust valve e-latch rocker arm mechanism is loaded,preventing the latch pin from moving. The solenoid current (plot 1408)increases until a maximum current is reached, generating an inductivesignature indicative of no latch pin movement. Because no latch pinmovement is detected during the solenoid energization, it is inferredthat the exhaust valve latch pin remains in the engaged position (plot1410) and that the cylinder is in an exhaust stroke. The identificationof the exhaust stroke enables the controller to determine theorientation of the camshaft relative to the known crankshaft position.

In the second example, the cylinder is in a compression stroke when theexhaust valve solenoid is energized at time t2. With the cylinder in thecompression stroke, the exhaust cam is on its base circle, with a lobelift of zero at time t2 (dashed plot 1405). The exhaust valve rocker armmechanism is unloaded, allowing the latch pin to move in response to thesolenoid energization. The solenoid current increases and thenmomentarily decreases until a local minimum is reached at time t3(dashed plot 1409), indicating that the latch pin has moved from theengaged to the disengaged position (dashed plot 1411). Because latch pinmovement is detected during the solenoid energization, it is inferredthat the cylinder is in a compression stroke. The identification of thecompression stroke enables the controller to determine the orientationof the camshaft relative to the known crankshaft position.

Because valve deactivation is not desired, in the second example, asecond voltage pulse of the opposite polarity to the first voltage pulse(dashed plot 1407) is supplied to the exhaust valve solenoid before theexhaust cam moves off of the base circle. As such, the exhaust valvelatch pin moves back to the engaged position (dashed plot 1411), asshown by the exhaust valve solenoid current reaching a local minimum attime t5 (dashed plot 1409). In this way, the camshaft position isdetermined without output of a camshaft position sensor by using theinductive signature of an exhaust valve e-latch solenoid to determinecylinder stroke.

FIG. 15 shows an example graph 1500 of determining crankshaft andcamshaft position in a fixed cam four-cylinder engine based on aninductive signature of an e-latch rocker arm mechanism solenoid and anoutput of a crankshaft position sensor, such as according to the methodof FIG. 10. Although the example of graph 1500 shows using intake valvedeactivation mechanisms to determine the crankshaft and camshaftpositions, it should be understood that exhaust valve deactivationmechanisms may alternatively be used. Intake valve solenoid voltage ofcylinder 1 is shown in plot 1502, intake valve solenoid current ofcylinder 1 is shown in plot 1504, intake valve solenoid voltage ofcylinder 2 is shown in plot 1506, intake valve solenoid current ofcylinder 2 is shown in plot 1508, intake valve solenoid voltage ofcylinder 3 is shown in plot 1510, intake valve solenoid current ofcylinder 3 is shown in plot 1512, intake valve solenoid voltage ofcylinder 4 is shown in plot 1514, intake valve solenoid current ofcylinder 4 is shown in plot 1516, and output of a crankshaft positionsensor (e.g., Hall effect sensor 120 of FIG. 1) is shown in plot 1518.For all of the above, the horizontal axis represents time, with timeincreasing along the horizontal axis from left to right. The verticalaxis represents each labeled parameter, with the value of the labeledparameter increasing along the vertical axis from bottom to top. In theexample of graph 1500, the engine does not include camshaft positionsensors.

Prior to time t1, the engine is started from rest, and the crankshaftposition and camshaft position are unknown. As such, an enginecontroller (e.g., controller 12 of FIG. 1) cannot accurately time fueland spark delivery. Additionally, each intake valve latch pin is knownto be in an engaged position (e.g., each intake valve e-latch rocker armmechanism is latched).

At time t2, the intake valve e-latch solenoid of each cylinder isenergized with a voltage pulse of a first (e.g., positive) polarity(plots 1502, 1506, 1510, and 1514). During the energization, the currentof each solenoid is monitored for an inductive signature indicative ofmovement of a corresponding latch pin. At time t3, local minima in thesolenoid current of cylinder 1 (plot 1504), the solenoid current ofcylinder 3 (plot 1512), and the solenoid current of cylinder 4 (plot1516) indicate the corresponding latch pins have moved (e.g., from theengaged position to a disengaged position). The steady current increaseand lack of local minimum of the solenoid of cylinder 2 indicates thatthe intake valve latch pin of cylinder 2 has not moved. As such, thecontroller infers that an intake cam of cylinder 2 is on its lobe,making cylinder 2 in an intake stroke.

Between time t3 and time t4, there is a gap in the crankshaft positionsensor output, representing missing teeth on a pulsewheel coupled to thecrankshaft. Due to the gap in the output, at time t4, when the squarewave signal returns, a crankshaft reference edge is identified (asdescribed with respect to FIG. 8). Due a known relationship between thecrankshaft position and the intake stroke of cylinder 2, the controllermay infer that the identified crankshaft reference edge is correct andnot due to a missed signal. The crankshaft reference edge corresponds toa known rotational orientation of the crankshaft, enabling thecrankshaft position to be determined. Further, due to a knownrelationship between the crankshaft position, cylinder stroke, and thecamshaft position, the camshaft position is determined relative to thecrankshaft position.

In the example of FIG. 15, intake valve deactivation during the enginestart is desired, and the intake valve latch pins of cylinders 1, 3, and4 have been actuated into the disengaged position, thereby deactivatingthe corresponding intake valves by time t3. However, the intake valve ofcylinder 2 remains in the engaged position. Therefore, while the intakecam of cylinder 2 is on base circle (not shown) at time t5, the intakevalve solenoid of cylinder 2 is re-energized with a voltage pulse of thefirst polarity (plot 1506) in order to move the intake valve latch pinof cylinder 2 to the disengaged position. The latch pin movement isconfirmed based on the momentary decrease in the intake valve solenoidcurrent of cylinder 2 (plot 1508) during the energization. However, inother examples, the latch pins of cylinders 1, 3, and 4 may be returnedto their starting positions when a change in the valve operational stateis not desired.

In this way, by inferring the presence of absence of movement of a latchpin of a cylinder valve deactivation mechanism based on an electriccurrent signature of an associated solenoid, the motion of the latch pincan be correlated with VDE operations. The technical aspect of verifyingif a latch pin moved when the associated solenoid was energized is thatthe cylinder valve deactivation mechanism can be reliably diagnosed withreduced reliance on dedicated sensors. By diagnosing and mitigatingissues associated with VDE mechanism degradation in a timely fashion,engine misfire occurrence can be reduced while also extending the fueleconomy benefits of VDE operation. By performing the diagnostic duringidling conditions following key-on, the diagnostic can be completedbefore the VDE mechanism is operated on a drive cycle. By additionallyor alternatively performing the diagnostic opportunistically over adrive cycle while the VDE mechanism is operated as a function ofchanging engine speed-load, the diagnostic can be completed withouthaving to intrusively command undesired VDE states. The technical effectof correlating the expected motion of the latch pin with the position ofa cam actuating a corresponding cylinder valve is that a camshaftposition can be learned with reduced reliance on a camshaft positionsensor. In addition, the correlation can be used to identify a pistonstroke for a cylinder and infer the state of a corresponding cylindervalve or associated rocker arm. By learning a camshaft and crankshafttiming based on the latch pin movement, fuel can be delivered to anengine more accurately, particularly during an engine restart event.Likewise, by placing valves in a target state during an engine start,such as by placing intake and exhaust valves of at least a firstcylinder to fire during an engine restart in a desired state ofactivation or deactivation, a timing of cylinder fuel delivery can beoptimized. By improving engine combustion torque generation, enginestartability is improved. By learning camshaft position, crankshaftposition, and valve or rocker arm state with reduced need for dedicatedsensors, costs can be reduced. In addition, the output of existingsensors can be corroborated. Overall, the performance of an engineconfigured with selective cylinder deactivation can be improved.

In one example, a method comprises: latching and unlatching anelectrically-actuated latch pin of a cylinder valve deactivationmechanism coupled to a valve of a cylinder as engine load varies; andindicating degradation of the cylinder valve deactivation mechanismbased on inferred latch pin movement during the latching and unlatching.In the preceding example, additionally or optionally, the latch pin iselectrically actuated by a solenoid, the method further comprising,inferring latch pin movement based on an electrical current signature ofthe solenoid, the electrical current signature including one or more ofa position of peaks and valleys of an electrical current of thesolenoid, and a slope of the electrical current. In any or all of thepreceding examples, additionally or optionally, the latch pin iselectrically actuated while a cam coupled to the cylinder valve is at abase circle position. In any or all of the preceding examples,additionally or optionally, the latching and unlatching as engine loadvaries includes unlatching the latch pin by energizing the solenoid withvoltage of a first polarity to deactivate the valve responsive to alower than threshold engine load, and latching the latch pin byenergizing the solenoid with voltage of a second polarity to reactivatethe valve responsive to a higher than threshold engine load. In any orall of the preceding examples, additionally or optionally, theindicating includes indicating degradation responsive to an absence oflatch pin movement during the latching or the unlatching when the cam isat the base circle position. In any or all of the preceding examples,additionally or optionally, the latching and unlatching is during adrive cycle, the method further comprising: responsive to the indicationof degradation when latching is attempted, maintaining the cylinderdeactivated over a remainder of the drive cycle; and responsive to theindication of degradation when unlatching is attempted, disablingdeactivating the cylinder responsive to lower than threshold engine loadlater in the drive cycle. In any or all of the preceding examples,additionally or optionally, the latching and unlatching is performedwhile engine speed is above an idling speed. In any or all of thepreceding examples, the method additionally or optionally furthercomprises learning a plurality of latch pin movement parameters based onthe electrical current signature of the solenoid; and adjusting anelectrical current applied to the solenoid during a subsequent latchingand unlatching of the latch pin based on the learned plurality of latchpin movement parameters. In any or all of the preceding examples,additionally or optionally, the learning includes learning a responsetime of the solenoid based on the electrical current signature, andwherein the adjusting includes adjusting a timing of energizing thesolenoid based on the learned response time. In any or all of thepreceding examples, additionally or optionally, the learning includeslearning an impact velocity applied by the latch pin to a final positionduring the latching, and wherein the adjusting includes adjusting apulse-width signal commanded to energize the solenoid based on thelearned impact velocity.

As another example, a method for an engine comprises: energizing asolenoid of a cylinder valve deactivation mechanism to actuate a latchpin to one of an engaged and a disengaged position based on engine loadover a drive cycle; diagnosing the valve deactivation mechanism based onlatch pin movement, inferred from an inductive signature of thesolenoid, while actuating the latch pin; and adjusting an energizationcurrent applied to the solenoid based on the diagnosing and furtherbased on the inductive signature. In the preceding example, additionallyor optionally, the energizing is performed while a cam coupled to thecylinder valve is at a base circle position, and the energizingincludes: responsive to a lower than a threshold engine load,deactivating the cylinder valve by energizing the solenoid with a firstpolarity of voltage to disengage the latch pin; and responsive to ahigher than the threshold engine load, activating the cylinder valve byenergizing the solenoid with a second polarity of voltage, opposite ofthe first polarity of voltage, to engage the latch pin. In any or all ofthe preceding examples, additionally or optionally, the diagnosingincludes: inferring a presence or an absence of the latch pin movementbased on the inductive signature of the solenoid, the inductivesignature including one or more of a position of current peaks andvalleys, and a rate of change of the inductive signature over a time ofthe energizing the solenoid. In any or all of the preceding examples,additionally or optionally, the diagnosing includes: indicating that themechanism is degraded responsive to absence of latch pin movement duringthe energizing; and indicating that the mechanism is not degradedresponsive to presence of latch pin movement during the energizing. Inany or all of the preceding examples, additionally or optionally,adjusting the energization current includes: responsive to theindication of degradation when the latch pin is in the disengagedposition, maintaining the cylinder deactivated over a remainder of thedrive cycle; and responsive to the indication of degradation when thelatch pin is in the engaged position, maintaining the cylinder activeover the remainder of the drive cycle. In any or all of the precedingexamples, additionally or optionally, adjusting the energization currentincludes: advancing a timing of applying the energization current as aresponse time of the latch pin, inferred from the inductive signature,increases; and decreasing a magnitude of the energization current as alatching force, inferred from the inductive signature, increases.

As another example, an engine system comprises: an engine cylinderincluding an intake valve; a cam mounted on a camshaft for opening andclosing the intake valve; a valve deactivation mechanism coupled to theintake valve, the mechanism including a rocker arm assembly and a latchpin, an inner arm of the rocker arm assembly coupled to the cam via acam follower and coupled to a stem of the intake valve, an outer arm ofthe rocker arm assembly coupled to the latch pin, the inner armengagable to the outer arm via the latch pin; an electric solenoidcoupled to the latch pin; an engine speed sensor; and a controller withcomputer readable instructions that when executed cause the controllerto: responsive to a higher than a threshold engine load during a drivecycle, energize the solenoid to actuate the latch pin to a latchedposition where the inner arm is engaged to the outer arm via the latchpin, and where the cylinder valve can lift via concerted movement of theouter arm and inner arm of the rocker arm assembly; responsive to alower than the threshold engine load during the drive cycle, energizethe solenoid to actuate the latch pin to an unlatched position where theinner arm is disengaged from the outer arm, and where the cylinder valvecannot be lifted; measure an induction current generated by the solenoidupon energization; infer a presence or an absence of movement of thelatch pin between the latched position and the unlatched position uponthe energization based on the measured induction current; and indicatedegradation of the valve deactivation mechanism responsive to theinferred absence of movement of the latch pin. In the preceding example,additionally or optionally, the controller includes further instructionsthat when executed cause the controller to: responsive to the indicationof degradation of the valve deactivation mechanism when the latch pin isin the latched position, maintain the latch pin in the latched positioneven while the engine load is lower than the threshold engine load. Inany or all of the preceding examples, additionally or optionally, thecontroller includes further instructions that when executed cause thecontroller to: responsive to the indication of degradation of the valvedeactivation mechanism when the latch pin is in the unlatched position,maintain the latch pin in the unlatched position even while the engineload is higher than the threshold engine load. In any or all of thepreceding examples, additionally or optionally, the controller includesfurther instructions that when executed cause the controller to: infer aplurality of latch pin movement parameters based on the inductioncurrent, the plurality of parameters including a response time of and alatching force applied by the latch pin; and adjust an energizationcurrent applied to the solenoid during subsequent latch pin actuatingbased on the inferred plurality of latch pin movement parameters, atiming of current application advanced as the response time increases, amagnitude of the current application decreased as the latching forceincreases.

In another representation, a method for an engine comprises: actuating alatch pin of a valve deactivation mechanism based on engine load;inferring a presence or an absence of latch pin movement during theactuating; and indicating degradation of the cylinder valve deactivationmechanism based on the inferred movement. In the preceding example,additionally or optionally, the valve deactivation mechanism is coupledto a cam-actuated cylinder valve, and actuating the latch pin includesenergizing a solenoid coupled to the latch pin with a voltage pulse whenthe cam is on base circle. In any or all of the preceding examples,additionally or optionally, inferring the presence or the absence oflatch pin movement during the actuating is based on a current of thesolenoid measured during the energizing. In any or all of the precedingexamples, additionally or optionally, inferring the presence or theabsence of latch pin movement during the actuating based on the currentof the solenoid measured during the energizing comprises: inferring thepresence of movement based on a presence of a local minimum in thecurrent as the current increases to a maximum; and inferring the absenceof movement based on an absence of the local minimum in the current asthe current increases to the maximum. In any or all of the precedingexamples, additionally or optionally, actuating the latch pin based onthe engine load comprises: actuating the latch pin to an engagedposition wherein the cylinder valve is active in response to the engineload meeting or exceeding a threshold; and actuating the latch pin to adisengaged position wherein the cylinder valve is deactivated inresponse to the engine load decreasing below the threshold. In any orall of the preceding examples, additionally or optionally, indicatingdegradation of the cylinder valve deactivation mechanism based on theinferred movement comprises: indicating degradation of the valvedeactivation mechanism in response to the absence of movement; and notindicating degradation of the valve deactivation mechanism in responseto the presence of movement.

Note that the example control and estimation routines included hereincan be used with various engine and/or vehicle system configurations.The control methods and routines disclosed herein may be stored asexecutable instructions in non-transitory memory and may be carried outby the control system including the controller in combination with thevarious sensors, actuators, and other engine hardware. The specificroutines described herein may represent one or more of any number ofprocessing strategies such as event-driven, interrupt-driven,multi-tasking, multi-threading, and the like. As such, various actions,operations, and/or functions illustrated may be performed in thesequence illustrated, in parallel, or in some cases omitted. Likewise,the order of processing is not necessarily required to achieve thefeatures and advantages of the example embodiments described herein, butis provided for ease of illustration and description. One or more of theillustrated actions, operations and/or functions may be repeatedlyperformed depending on the particular strategy being used. Further, thedescribed actions, operations and/or functions may graphically representcode to be programmed into non-transitory memory of the computerreadable storage medium in the engine control system, where thedescribed actions are carried out by executing the instructions in asystem including the various engine hardware components in combinationwith the electronic controller.

It will be appreciated that the configurations and routines disclosedherein are exemplary in nature, and that these specific embodiments arenot to be considered in a limiting sense, because numerous variationsare possible. For example, the above technology can be applied to V-6,I-4, I-6, V-12, opposed 4, and other engine types. The subject matter ofthe present disclosure includes all novel and non-obvious combinationsand sub-combinations of the various systems and configurations, andother features, functions, and/or properties disclosed herein.

The following claims particularly point out certain combinations andsub-combinations regarded as novel and non-obvious. These claims mayrefer to “an” element or “a first” element or the equivalent thereof.Such claims should be understood to include incorporation of one or moresuch elements, neither requiring nor excluding two or more suchelements. Other combinations and sub-combinations of the disclosedfeatures, functions, elements, and/or properties may be claimed throughamendment of the present claims or through presentation of new claims inthis or a related application. Such claims, whether broader, narrower,equal, or different in scope to the original claims, also are regardedas included within the subject matter of the present disclosure.

1. A method for an engine, comprising: latching and unlatching anelectrically-actuated latch pin of a cylinder valve deactivationmechanism coupled to a valve of a cylinder as engine load varies; andindicating degradation of the cylinder valve deactivation mechanismbased on inferred latch pin movement during the latching and unlatching.2. The method of claim 1, wherein the latch pin is electrically actuatedby a solenoid, the method further comprising, inferring latch pinmovement based on an electrical current signature of the solenoid, theelectrical current signature including one or more of a position ofpeaks and valleys of an electrical current of the solenoid, and a slopeof the electrical current.
 3. The method of claim 2, wherein the latchpin is electrically actuated while a cam coupled to the cylinder valveis at a base circle position.
 4. The method of claim 3, wherein thelatching and unlatching as engine load varies includes unlatching thelatch pin by energizing the solenoid with voltage of a first polarity todeactivate the valve responsive to a lower than threshold engine load,and latching the latch pin by energizing the solenoid with voltage of asecond polarity to reactivate the valve responsive to a higher thanthreshold engine load.
 5. The method of claim 4, wherein the indicatingincludes indicating degradation responsive to an absence of latch pinmovement during the latching or the unlatching when the cam is at thebase circle position.
 6. The method of claim 5, wherein the latching andunlatching is during a drive cycle, the method further comprising:responsive to the indication of degradation when latching is attempted,maintaining the cylinder deactivated over a remainder of the drivecycle; and responsive to the indication of degradation when unlatchingis attempted, disabling deactivating the cylinder responsive to lowerthan threshold engine load later in the drive cycle.
 7. The method ofclaim 1, wherein the latching and unlatching is performed while enginespeed is above an idling speed.
 8. The method of claim 2, furthercomprising: learning a plurality of latch pin movement parameters basedon the electrical current signature of the solenoid; and adjusting anelectrical current applied to the solenoid during a subsequent latchingand unlatching of the latch pin based on the learned plurality of latchpin movement parameters.
 9. The method of claim 8, wherein the learningincludes learning a response time of the solenoid based on theelectrical current signature, and wherein the adjusting includesadjusting a timing of energizing the solenoid based on the learnedresponse time.
 10. The method of claim 8, wherein the learning includeslearning an impact velocity applied by the latch pin to a final positionduring the latching, and wherein the adjusting includes adjusting apulse-width signal commanded to energize the solenoid based on thelearned impact velocity.
 11. A method for an engine, comprising:energizing a solenoid of a cylinder valve deactivation mechanism toactuate a latch pin to one of an engaged and a disengaged position basedon engine load over a drive cycle; diagnosing the valve deactivationmechanism based on latch pin movement, inferred from an inductivesignature of the solenoid, while actuating the latch pin; and adjustingan energization current applied to the solenoid based on the diagnosingand further based on the inductive signature.
 12. The method of claim11, wherein the energizing is performed while a cam coupled to thecylinder valve is at a base circle position, and the energizingincludes: responsive to a lower than a threshold engine load,deactivating the cylinder valve by energizing the solenoid with a firstpolarity of voltage to disengage the latch pin; and responsive to ahigher than the threshold engine load, activating the cylinder valve byenergizing the solenoid with a second polarity of voltage, opposite ofthe first polarity of voltage, to engage the latch pin.
 13. The methodof claim 11, wherein the diagnosing includes: inferring a presence or anabsence of the latch pin movement based on the inductive signature ofthe solenoid, the inductive signature including one or more of aposition of current peaks and valleys, and a rate of change of theinductive signature over a time of the energizing the solenoid.
 14. Themethod of claim 13, wherein the diagnosing includes: indicating that themechanism is degraded responsive to absence of latch pin movement duringthe energizing; and indicating that the mechanism is not degradedresponsive to presence of latch pin movement during the energizing. 15.The method of claim 14, wherein adjusting the energization currentincludes: responsive to the indication of degradation when the latch pinis in the disengaged position, maintaining the cylinder deactivated overa remainder of the drive cycle; and responsive to the indication ofdegradation when the latch pin is in the engaged position, maintainingthe cylinder active over the remainder of the drive cycle.
 16. Themethod of claim 13, wherein adjusting the energization current includes:advancing a timing of applying the energization current as a responsetime of the latch pin, inferred from the inductive signature, increases;and decreasing a magnitude of the energization current as a latchingforce, inferred from the inductive signature, increases.
 17. An enginesystem, comprising: an engine cylinder including an intake valve; a cammounted on a camshaft for opening and closing the intake valve; a valvedeactivation mechanism coupled to the intake valve, the mechanismincluding a rocker arm assembly and a latch pin, an inner arm of therocker arm assembly coupled to the cam via a cam follower and coupled toa stem of the intake valve, an outer arm of the rocker arm assemblycoupled to the latch pin, the inner arm engagable to the outer arm viathe latch pin; an electric solenoid coupled to the latch pin; an enginespeed sensor; and a controller with computer readable instructions thatwhen executed cause the controller to: responsive to a higher than athreshold engine load during a drive cycle, energize the solenoid toactuate the latch pin to a latched position where the inner arm isengaged to the outer arm via the latch pin, and where the cylinder valvecan lift via concerted movement of the outer arm and inner arm of therocker arm assembly; responsive to a lower than the threshold engineload during the drive cycle, energize the solenoid to actuate the latchpin to an unlatched position where the inner arm is disengaged from theouter arm, and where the cylinder valve cannot be lifted; measure aninduction current generated by the solenoid upon energization; infer apresence or an absence of movement of the latch pin between the latchedposition and the unlatched position upon the energization based on themeasured induction current; and indicate degradation of the valvedeactivation mechanism responsive to the inferred absence of movement ofthe latch pin.
 18. The system of claim 17, wherein the controllerincludes further instructions that when executed cause the controllerto: responsive to the indication of degradation of the valvedeactivation mechanism when the latch pin is in the latched position,maintain the latch pin in the latched position even while the engineload is lower than the threshold engine load.
 19. The system of claim17, wherein the controller includes further instructions that whenexecuted cause the controller to: responsive to the indication ofdegradation of the valve deactivation mechanism when the latch pin is inthe unlatched position, maintain the latch pin in the unlatched positioneven while the engine load is higher than the threshold engine load. 20.The system of claim 17, wherein the controller includes furtherinstructions that when executed cause the controller to: infer aplurality of latch pin movement parameters based on the inductioncurrent, the plurality of parameters including a response time of and alatching force applied by the latch pin; and adjust an energizationcurrent applied to the solenoid during subsequent latch pin actuatingbased on the inferred plurality of latch pin movement parameters, atiming of current application advanced as the response time increases, amagnitude of the current application decreased as the latching forceincreases.